diff --git a/lib/prism/node_ext.rb b/lib/prism/node_ext.rb
index 12567b8abf..a9a0115a09 100644
--- a/lib/prism/node_ext.rb
+++ b/lib/prism/node_ext.rb
@@ -71,13 +71,6 @@ module Prism
     end
   end
 
-  class IntegerNode < Node
-    # Returns the value of the node as a Ruby Integer.
-    def value
-      Integer(slice)
-    end
-  end
-
   class RationalNode < Node
     # Returns the value of the node as a Ruby Rational.
     def value
diff --git a/prism/config.yml b/prism/config.yml
index 15b7d4d0e9..33abcc623c 100644
--- a/prism/config.yml
+++ b/prism/config.yml
@@ -1867,6 +1867,9 @@ nodes:
       - name: flags
         type: flags
         kind: IntegerBaseFlags
+      - name: value
+        type: integer
+        comment: The value of the integer literal as a number.
     comment: |
       Represents an integer number literal.
 
diff --git a/prism/extension.h b/prism/extension.h
index 048f4b427f..6e5a345012 100644
--- a/prism/extension.h
+++ b/prism/extension.h
@@ -7,9 +7,9 @@
 #include <ruby/encoding.h>
 #include "prism.h"
 
-VALUE pm_source_new(pm_parser_t *parser, rb_encoding *encoding);
-VALUE pm_token_new(pm_parser_t *parser, pm_token_t *token, rb_encoding *encoding, VALUE source);
-VALUE pm_ast_new(pm_parser_t *parser, pm_node_t *node, rb_encoding *encoding, VALUE source);
+VALUE pm_source_new(const pm_parser_t *parser, rb_encoding *encoding);
+VALUE pm_token_new(const pm_parser_t *parser, const pm_token_t *token, rb_encoding *encoding, VALUE source);
+VALUE pm_ast_new(const pm_parser_t *parser, const pm_node_t *node, rb_encoding *encoding, VALUE source);
 
 void Init_prism_api_node(void);
 void Init_prism_pack(void);
diff --git a/prism/prism.c b/prism/prism.c
index cf893c6eef..a1b2bf74e2 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -3803,12 +3803,25 @@ pm_integer_node_create(pm_parser_t *parser, pm_node_flags_t base, const pm_token
     assert(token->type == PM_TOKEN_INTEGER);
     pm_integer_node_t *node = PM_ALLOC_NODE(parser, pm_integer_node_t);
 
-    *node = (pm_integer_node_t) {{
-        .type = PM_INTEGER_NODE,
-        .flags = base | PM_NODE_FLAG_STATIC_LITERAL,
-        .location = PM_LOCATION_TOKEN_VALUE(token)
-    }};
+    *node = (pm_integer_node_t) {
+        {
+            .type = PM_INTEGER_NODE,
+            .flags = base | PM_NODE_FLAG_STATIC_LITERAL,
+            .location = PM_LOCATION_TOKEN_VALUE(token)
+        },
+        .value = { 0 }
+    };
 
+    pm_number_base_t number_base;
+    switch (base) {
+        case PM_INTEGER_BASE_FLAGS_BINARY: number_base = PM_NUMBER_BASE_BINARY; break;
+        case PM_INTEGER_BASE_FLAGS_OCTAL: number_base = PM_NUMBER_BASE_OCTAL; break;
+        case PM_INTEGER_BASE_FLAGS_DECIMAL: number_base = PM_NUMBER_BASE_DECIMAL; break;
+        case PM_INTEGER_BASE_FLAGS_HEXADECIMAL: number_base = PM_NUMBER_BASE_HEXADECIMAL; break;
+        default: assert(false && "unreachable");
+    }
+
+    pm_number_parse(&node->value, number_base, token->start, token->end);
     return node;
 }
 
@@ -14281,6 +14294,9 @@ static inline void
 parse_negative_numeric(pm_node_t *node) {
     switch (PM_NODE_TYPE(node)) {
         case PM_INTEGER_NODE:
+            node->location.start--;
+            ((pm_integer_node_t *) node)->value.negative = true;
+            break;
         case PM_FLOAT_NODE:
             node->location.start--;
             break;
diff --git a/prism/templates/ext/prism/api_node.c.erb b/prism/templates/ext/prism/api_node.c.erb
index 55867f078c..38288918d8 100644
--- a/prism/templates/ext/prism/api_node.c.erb
+++ b/prism/templates/ext/prism/api_node.c.erb
@@ -12,13 +12,13 @@ static VALUE rb_cPrism<%= node.name %>;
 <%- end -%>
 
 static VALUE
-pm_location_new(pm_parser_t *parser, const uint8_t *start, const uint8_t *end) {
+pm_location_new(const pm_parser_t *parser, const uint8_t *start, const uint8_t *end) {
     uint64_t value = ((((uint64_t) (start - parser->start)) << 32) | ((uint32_t) (end - start)));
     return ULL2NUM(value);
 }
 
 VALUE
-pm_token_new(pm_parser_t *parser, pm_token_t *token, rb_encoding *encoding, VALUE source) {
+pm_token_new(const pm_parser_t *parser, const pm_token_t *token, rb_encoding *encoding, VALUE source) {
     ID type = rb_intern(pm_token_type_name(token->type));
     VALUE location = pm_location_new(parser, token->start, token->end);
 
@@ -33,13 +33,30 @@ pm_token_new(pm_parser_t *parser, pm_token_t *token, rb_encoding *encoding, VALU
 }
 
 static VALUE
-pm_string_new(pm_string_t *string, rb_encoding *encoding) {
+pm_string_new(const pm_string_t *string, rb_encoding *encoding) {
     return rb_enc_str_new((const char *) pm_string_source(string), pm_string_length(string), encoding);
 }
 
+static VALUE
+pm_integer_new(const pm_number_t *number) {
+    VALUE result = UINT2NUM(number->head.value);
+    size_t shift = 0;
+
+    for (const pm_number_node_t *node = number->head.next; node != NULL; node = node->next) {
+        VALUE receiver = rb_funcall(UINT2NUM(node->value), rb_intern("<<"), 1, ULONG2NUM(++shift * 32));
+        result = rb_funcall(receiver, rb_intern("|"), 1, result);
+    }
+
+    if (number->negative) {
+        result = rb_funcall(result, rb_intern("-@"), 0);
+    }
+
+    return result;
+}
+
 // Create a Prism::Source object from the given parser, after pm_parse() was called.
 VALUE
-pm_source_new(pm_parser_t *parser, rb_encoding *encoding) {
+pm_source_new(const pm_parser_t *parser, rb_encoding *encoding) {
     VALUE source_string = rb_enc_str_new((const char *) parser->start, parser->end - parser->start, encoding);
 
     VALUE offsets = rb_ary_new_capa(parser->newline_list.size);
@@ -53,12 +70,12 @@ pm_source_new(pm_parser_t *parser, rb_encoding *encoding) {
 
 typedef struct pm_node_stack_node {
     struct pm_node_stack_node *prev;
-    pm_node_t *visit;
+    const pm_node_t *visit;
     bool visited;
 } pm_node_stack_node_t;
 
 static void
-pm_node_stack_push(pm_node_stack_node_t **stack, pm_node_t *visit) {
+pm_node_stack_push(pm_node_stack_node_t **stack, const pm_node_t *visit) {
     pm_node_stack_node_t *node = malloc(sizeof(pm_node_stack_node_t));
     node->prev = *stack;
     node->visit = visit;
@@ -66,10 +83,10 @@ pm_node_stack_push(pm_node_stack_node_t **stack, pm_node_t *visit) {
     *stack = node;
 }
 
-static pm_node_t *
+static const pm_node_t *
 pm_node_stack_pop(pm_node_stack_node_t **stack) {
     pm_node_stack_node_t *current = *stack;
-    pm_node_t *visit = current->visit;
+    const pm_node_t *visit = current->visit;
 
     *stack = current->prev;
     free(current);
@@ -78,7 +95,7 @@ pm_node_stack_pop(pm_node_stack_node_t **stack) {
 }
 
 VALUE
-pm_ast_new(pm_parser_t *parser, pm_node_t *node, rb_encoding *encoding, VALUE source) {
+pm_ast_new(const pm_parser_t *parser, const pm_node_t *node, rb_encoding *encoding, VALUE source) {
     ID *constants = calloc(parser->constant_pool.size, sizeof(ID));
 
     for (uint32_t index = 0; index < parser->constant_pool.size; index++) {
@@ -108,7 +125,7 @@ pm_ast_new(pm_parser_t *parser, pm_node_t *node, rb_encoding *encoding, VALUE so
                 continue;
             }
 
-            pm_node_t *node = node_stack->visit;
+            const pm_node_t *node = node_stack->visit;
             node_stack->visited = true;
 
             switch (PM_NODE_TYPE(node)) {
@@ -136,7 +153,7 @@ pm_ast_new(pm_parser_t *parser, pm_node_t *node, rb_encoding *encoding, VALUE so
             }
 #line <%= __LINE__ + 1 %> "<%= File.basename(__FILE__) %>"
         } else {
-            pm_node_t *node = pm_node_stack_pop(&node_stack);
+            const pm_node_t *node = pm_node_stack_pop(&node_stack);
 
             switch (PM_NODE_TYPE(node)) {
                 <%- nodes.each do |node| -%>
@@ -193,6 +210,9 @@ pm_ast_new(pm_parser_t *parser, pm_node_t *node, rb_encoding *encoding, VALUE so
                     <%- when Prism::FlagsField -%>
 #line <%= __LINE__ + 1 %> "<%= File.basename(__FILE__) %>"
                     argv[<%= index %>] = ULONG2NUM(node->flags & ~PM_NODE_FLAG_COMMON_MASK);
+                    <%- when Prism::IntegerField -%>
+#line <%= __LINE__ + 1 %> "<%= File.basename(__FILE__) %>"
+                    argv[<%= index %>] = pm_integer_new(&cast-><%= field.name %>);
                     <%- else -%>
                     <%- raise -%>
                     <%- end -%>
diff --git a/prism/templates/include/prism/ast.h.erb b/prism/templates/include/prism/ast.h.erb
index 13b923b029..e75fdd51ab 100644
--- a/prism/templates/include/prism/ast.h.erb
+++ b/prism/templates/include/prism/ast.h.erb
@@ -183,6 +183,7 @@ typedef struct pm_<%= node.human %> {
     when Prism::LocationField, Prism::OptionalLocationField then "pm_location_t #{field.name}"
     when Prism::UInt8Field then "uint8_t #{field.name}"
     when Prism::UInt32Field then "uint32_t #{field.name}"
+    when Prism::IntegerField then "pm_number_t #{field.name}"
     else raise field.class.name
     end
     %>;
diff --git a/prism/templates/lib/prism/dot_visitor.rb.erb b/prism/templates/lib/prism/dot_visitor.rb.erb
index fc3dd4b223..7689bc913f 100644
--- a/prism/templates/lib/prism/dot_visitor.rb.erb
+++ b/prism/templates/lib/prism/dot_visitor.rb.erb
@@ -133,7 +133,7 @@ module Prism
       else
         table.field("<%= field.name %>", "[]")
       end
-      <%- when Prism::StringField, Prism::ConstantField, Prism::OptionalConstantField, Prism::UInt8Field, Prism::UInt32Field, Prism::ConstantListField -%>
+      <%- when Prism::StringField, Prism::ConstantField, Prism::OptionalConstantField, Prism::UInt8Field, Prism::UInt32Field, Prism::ConstantListField, Prism::IntegerField -%>
       table.field("<%= field.name %>", node.<%= field.name %>.inspect)
       <%- when Prism::LocationField -%>
       table.field("<%= field.name %>", location_inspect(node.<%= field.name %>))
diff --git a/prism/templates/lib/prism/dsl.rb.erb b/prism/templates/lib/prism/dsl.rb.erb
index d21cf53022..7c55fb10bc 100644
--- a/prism/templates/lib/prism/dsl.rb.erb
+++ b/prism/templates/lib/prism/dsl.rb.erb
@@ -8,6 +8,7 @@ module Prism
   #       [
   #         Prism::IntegerNode.new(
   #           Prism::IntegerBaseFlags::DECIMAL,
+  #           1,
   #           Prism::Location.new(source, 1, 1),
   #           source
   #         )
@@ -22,7 +23,7 @@ module Prism
   #     source = Prism::Source.new("[1]")
   #
   #     ArrayNode(
-  #       IntegerNode(Prism::IntegerBaseFlags::DECIMAL, Location(source, 1, 1)), source),
+  #       IntegerNode(Prism::IntegerBaseFlags::DECIMAL, 1, Location(source, 1, 1)), source),
   #       Location(source, 0, 1),
   #       Location(source, 2, 1),
   #       source
diff --git a/prism/templates/lib/prism/node.rb.erb b/prism/templates/lib/prism/node.rb.erb
index 2eb385c09a..df8f16a1e8 100644
--- a/prism/templates/lib/prism/node.rb.erb
+++ b/prism/templates/lib/prism/node.rb.erb
@@ -281,7 +281,7 @@ module Prism
         inspector << "<%= pointer %><%= field.name %>:\n"
         inspector << <%= field.name %>.inspect(inspector.child_inspector("<%= preadd %>")).delete_prefix(inspector.prefix)
       end
-      <%- when Prism::ConstantField, Prism::StringField, Prism::UInt8Field, Prism::UInt32Field -%>
+      <%- when Prism::ConstantField, Prism::StringField, Prism::UInt8Field, Prism::UInt32Field, Prism::IntegerField -%>
       inspector << "<%= pointer %><%= field.name %>: #{<%= field.name %>.inspect}\n"
       <%- when Prism::OptionalConstantField -%>
       if (<%= field.name %> = self.<%= field.name %>).nil?
diff --git a/prism/templates/lib/prism/serialize.rb.erb b/prism/templates/lib/prism/serialize.rb.erb
index 5193dfdeca..0214913c19 100644
--- a/prism/templates/lib/prism/serialize.rb.erb
+++ b/prism/templates/lib/prism/serialize.rb.erb
@@ -172,6 +172,17 @@ module Prism
         (n >> 1) ^ (-(n & 1))
       end
 
+      def load_integer
+        negative = io.getbyte != 0
+        length = load_varuint
+
+        value = 0
+        length.times { |index| value |= (load_varuint << (index * 32)) }
+
+        value = -value if negative
+        value
+      end
+
       def load_serialized_length
         io.read(4).unpack1("L")
       end
@@ -288,6 +299,7 @@ module Prism
               when Prism::OptionalLocationField then "load_optional_location"
               when Prism::UInt8Field then "io.getbyte"
               when Prism::UInt32Field, Prism::FlagsField then "load_varuint"
+              when Prism::IntegerField then "load_integer"
               else raise
               end
             } + ["location"]).join(", ") -%>)
@@ -323,6 +335,7 @@ module Prism
                 when Prism::OptionalLocationField then "load_optional_location"
                 when Prism::UInt8Field then "io.getbyte"
                 when Prism::UInt32Field, Prism::FlagsField then "load_varuint"
+                when Prism::IntegerField then "load_integer"
                 else raise
                 end
               } + ["location"]).join(", ") -%>)
diff --git a/prism/templates/src/node.c.erb b/prism/templates/src/node.c.erb
index 095a2b171e..bc5eca43a0 100644
--- a/prism/templates/src/node.c.erb
+++ b/prism/templates/src/node.c.erb
@@ -74,6 +74,8 @@ pm_node_destroy(pm_parser_t *parser, pm_node_t *node) {
             pm_node_list_free(parser, &cast-><%= field.name %>);
             <%- when Prism::ConstantListField -%>
             pm_constant_id_list_free(&cast-><%= field.name %>);
+            <%- when Prism::IntegerField -%>
+            pm_number_free(&cast-><%= field.name %>);
             <%- else -%>
             <%- raise -%>
             <%- end -%>
@@ -103,14 +105,6 @@ pm_node_memsize_node(pm_node_t *node, pm_memsize_t *memsize) {
         case <%= node.type %>: {
             pm_<%= node.human %>_t *cast = (pm_<%= node.human %>_t *) node;
             memsize->memsize += sizeof(*cast);
-            <%- if node.fields.any? { |f| f.is_a?(Prism::NodeListField) } -%>
-            // Node lists will add in their own sizes below.
-            memsize->memsize -= sizeof(pm_node_list_t) * <%= node.fields.count { |f| f.is_a?(Prism::NodeListField) } %>;
-            <%- end -%>
-            <%- if node.fields.any? { |f| f.is_a?(Prism::ConstantListField) } -%>
-            // Constant id lists will add in their own sizes below.
-            memsize->memsize -= sizeof(pm_constant_id_list_t) * <%= node.fields.count { |f| f.is_a?(Prism::ConstantListField) } %>;
-            <%- end -%>
             <%- node.fields.each do |field| -%>
             <%- case field -%>
             <%- when Prism::ConstantField, Prism::OptionalConstantField, Prism::UInt8Field, Prism::UInt32Field, Prism::FlagsField, Prism::LocationField, Prism::OptionalLocationField -%>
@@ -121,11 +115,13 @@ pm_node_memsize_node(pm_node_t *node, pm_memsize_t *memsize) {
                 pm_node_memsize_node((pm_node_t *)cast-><%= field.name %>, memsize);
             }
             <%- when Prism::StringField -%>
-            memsize->memsize += pm_string_memsize(&cast-><%= field.name %>);
+            memsize->memsize += (pm_string_memsize(&cast-><%= field.name %>) - sizeof(pm_string_t));
             <%- when Prism::NodeListField -%>
-            memsize->memsize += pm_node_list_memsize(&cast-><%= field.name %>, memsize);
+            memsize->memsize += (pm_node_list_memsize(&cast-><%= field.name %>, memsize) - sizeof(pm_node_list_t));
             <%- when Prism::ConstantListField -%>
-            memsize->memsize += pm_constant_id_list_memsize(&cast-><%= field.name %>);
+            memsize->memsize += (pm_constant_id_list_memsize(&cast-><%= field.name %>) - sizeof(pm_constant_id_list_t));
+            <%- when Prism::IntegerField -%>
+            memsize->memsize += (pm_number_memsize(&cast-><%= field.name %>) - sizeof(pm_number_t));
             <%- else -%>
             <%- raise -%>
             <%- end -%>
@@ -257,6 +253,29 @@ pm_dump_json(pm_buffer_t *buffer, const pm_parser_t *parser, const pm_node_t *no
             }
             <%- end -%>
             pm_buffer_append_byte(buffer, ']');
+            <%- when Prism::IntegerField -%>
+            {
+                const pm_number_t *number = &cast-><%= field.name %>;
+                if (number->length == 0) {
+                    if (number->negative) pm_buffer_append_byte(buffer, '-');
+                    pm_buffer_append_string(buffer, "%" PRIu32, number->head.value);
+                } else if (number->length == 1) {
+                    if (number->negative) pm_buffer_append_byte(buffer, '-');
+                    pm_buffer_append_format(buffer, "%" PRIu64, ((uint64_t) number->head.value) | (((uint64_t) number->head.next->value) << 32));
+                } else {
+                    pm_buffer_append_byte(buffer, '{');
+                    pm_buffer_append_format(buffer, "\"negative\": %s", number->negative ? "true" : "false");
+                    pm_buffer_append_string(buffer, ",\"values\":[", 11);
+
+                    const pm_number_node_t *node = &number->head;
+                    while (node != NULL) {
+                        pm_buffer_append_format(buffer, "%" PRIu32, node->value);
+                        node = node->next;
+                        if (node != NULL) pm_buffer_append_byte(buffer, ',');
+                    }
+                    pm_buffer_append_string(buffer, "]}", 2);
+                }
+            }
             <%- else -%>
             <%- raise %>
             <%- end -%>
diff --git a/prism/templates/src/prettyprint.c.erb b/prism/templates/src/prettyprint.c.erb
index c6dd5facef..799e8b91ef 100644
--- a/prism/templates/src/prettyprint.c.erb
+++ b/prism/templates/src/prettyprint.c.erb
@@ -126,6 +126,36 @@ prettyprint_node(pm_buffer_t *output_buffer, const pm_parser_t *parser, const pm
                 <%- end -%>
                 if (!found) pm_buffer_append_string(output_buffer, " nil", 4);
                 pm_buffer_append_byte(output_buffer, '\n');
+            <%- when Prism::IntegerField -%>
+                const pm_number_t *number = &cast-><%= field.name %>;
+                if (number->length == 0) {
+                    pm_buffer_append_byte(output_buffer, ' ');
+                    if (number->negative) pm_buffer_append_byte(output_buffer, '-');
+                    pm_buffer_append_string(output_buffer, "%" PRIu32 "\n", number->head.value);
+                } else if (number->length == 1) {
+                    pm_buffer_append_byte(output_buffer, ' ');
+                    if (number->negative) pm_buffer_append_byte(output_buffer, '-');
+                    pm_buffer_append_string(output_buffer, "%" PRIu64 "\n", ((uint64_t) number->head.value) | (((uint64_t) number->head.next->value) << 32));
+                } else {
+                    pm_buffer_append_byte(output_buffer, ' ');
+
+                    const pm_number_node_t *node = &number->head;
+                    uint32_t index = 0;
+
+                    while (node != NULL) {
+                        if (index != 0) pm_buffer_append_string(output_buffer, " | ", 3);
+                        pm_buffer_append_format(output_buffer, "%" PRIu32, node->value);
+
+                        if (index != 0) {
+                            pm_buffer_append_string(output_buffer, " << ", 4);
+                            pm_buffer_append_format(output_buffer, "%" PRIu32, index * 32);
+                        }
+
+                        node = node->next;
+                        index++;
+                    }
+                    pm_buffer_append_string(output_buffer, "]\n", 2);
+                }
             <%- else -%>
             <%- raise -%>
             <%- end -%>
diff --git a/prism/templates/src/serialize.c.erb b/prism/templates/src/serialize.c.erb
index 7c20e06ea9..cfa82d96f5 100644
--- a/prism/templates/src/serialize.c.erb
+++ b/prism/templates/src/serialize.c.erb
@@ -25,7 +25,7 @@ pm_serialize_location(const pm_parser_t *parser, const pm_location_t *location,
 }
 
 static void
-pm_serialize_string(pm_parser_t *parser, pm_string_t *string, pm_buffer_t *buffer) {
+pm_serialize_string(const pm_parser_t *parser, const pm_string_t *string, pm_buffer_t *buffer) {
     switch (string->type) {
         case PM_STRING_SHARED: {
             pm_buffer_append_byte(buffer, 1);
@@ -49,6 +49,16 @@ pm_serialize_string(pm_parser_t *parser, pm_string_t *string, pm_buffer_t *buffe
     }
 }
 
+static void
+pm_serialize_integer(const pm_number_t *number, pm_buffer_t *buffer) {
+    pm_buffer_append_byte(buffer, number->negative ? 1 : 0);
+    pm_buffer_append_varuint(buffer, pm_sizet_to_u32(number->length + 1));
+
+    for (const pm_number_node_t *node = &number->head; node != NULL; node = node->next) {
+        pm_buffer_append_varuint(buffer, node->value);
+    }
+}
+
 static void
 pm_serialize_node(pm_parser_t *parser, pm_node_t *node, pm_buffer_t *buffer) {
     pm_buffer_append_byte(buffer, (uint8_t) PM_NODE_TYPE(node));
@@ -115,6 +125,8 @@ pm_serialize_node(pm_parser_t *parser, pm_node_t *node, pm_buffer_t *buffer) {
             pm_buffer_append_varuint(buffer, ((pm_<%= node.human %>_t *)node)-><%= field.name %>);
             <%- when Prism::FlagsField -%>
             pm_buffer_append_varuint(buffer, (uint32_t)(node->flags & ~PM_NODE_FLAG_COMMON_MASK));
+            <%- when Prism::IntegerField -%>
+            pm_serialize_integer(&((pm_<%= node.human %>_t *)node)-><%= field.name %>, buffer);
             <%- else -%>
             <%- raise -%>
             <%- end -%>
diff --git a/prism/templates/template.rb b/prism/templates/template.rb
index 4576191701..be769c2ddd 100755
--- a/prism/templates/template.rb
+++ b/prism/templates/template.rb
@@ -254,6 +254,22 @@ module Prism
     end
   end
 
+  # This represents an arbitrarily-sized integer. When it gets to Ruby it will
+  # be an Integer.
+  class IntegerField < Field
+    def rbs_class
+      "Integer"
+    end
+
+    def rbi_class
+      "Integer"
+    end
+
+    def java_type
+      "VariableInteger"
+    end
+  end
+
   # This class represents a node in the tree, configured by the config.yml file
   # in YAML format. It contains information about the name of the node and the
   # various child nodes it contains.
@@ -315,6 +331,7 @@ module Prism
       when "uint8"      then UInt8Field
       when "uint32"     then UInt32Field
       when "flags"      then FlagsField
+      when "integer"    then IntegerField
       else raise("Unknown field type: #{name.inspect}")
       end
     end
diff --git a/prism/util/pm_number.c b/prism/util/pm_number.c
index d2733330a6..6f0a13ae8e 100644
--- a/prism/util/pm_number.c
+++ b/prism/util/pm_number.c
@@ -87,17 +87,11 @@ pm_number_parse_digit(const uint8_t character) {
  */
 PRISM_EXPORTED_FUNCTION void
 pm_number_parse(pm_number_t *number, pm_number_base_t base, const uint8_t *start, const uint8_t *end) {
-    switch (*start) {
-        case '-':
-            number->negative = true;
-        /* fallthrough */
-        case '+':
-            start++;
-            break;
-        default:
-            break;
-    }
+    // Ignore unary +. Unary + is parsed differently and will not end up here.
+    // Instead, it will modify the parsed number later.
+    if (*start == '+') start++;
 
+    // Determine the multiplier from the base, and skip past any prefixes.
     uint32_t multiplier;
     switch (base) {
         case PM_NUMBER_BASE_BINARY:
@@ -133,13 +127,29 @@ pm_number_parse(pm_number_t *number, pm_number_base_t base, const uint8_t *start
             break;
     }
 
-    for (pm_number_add(number, pm_number_parse_digit(*start++)); start < end; start++) {
+    // It's possible that we've consumed everything at this point if there is an
+    // invalid number. If this is the case, we'll just return 0.
+    if (start >= end) return;
+
+    // Add the first digit to the number.
+    pm_number_add(number, pm_number_parse_digit(*start++));
+
+    // Add the subsequent digits to the number.
+    for (; start < end; start++) {
         if (*start == '_') continue;
         pm_number_multiply(number, multiplier);
         pm_number_add(number, pm_number_parse_digit(*start));
     }
 }
 
+/**
+ * Return the memory size of the number.
+ */
+size_t
+pm_number_memsize(const pm_number_t *number) {
+    return sizeof(pm_number_t) + number->length * sizeof(pm_number_node_t);
+}
+
 /**
  * Recursively destroy the linked list of a number.
  */
diff --git a/prism/util/pm_number.h b/prism/util/pm_number.h
index c2507cf1df..04404ffa0d 100644
--- a/prism/util/pm_number.h
+++ b/prism/util/pm_number.h
@@ -84,6 +84,14 @@ typedef enum {
  */
 PRISM_EXPORTED_FUNCTION void pm_number_parse(pm_number_t *number, pm_number_base_t base, const uint8_t *start, const uint8_t *end);
 
+/**
+ * Return the memory size of the number.
+ *
+ * @param number The number to get the memory size of.
+ * @return The size of the memory associated with the number.
+ */
+size_t pm_number_memsize(const pm_number_t *number);
+
 /**
  * Free the internal memory of a number. This memory will only be allocated if
  * the number exceeds the size of a single node in the linked list.
diff --git a/test/prism/errors_test.rb b/test/prism/errors_test.rb
index 6c9463ee92..f4a19f83f2 100644
--- a/test/prism/errors_test.rb
+++ b/test/prism/errors_test.rb
@@ -966,8 +966,8 @@ module Prism
         ParametersNode(
           [RequiredParameterNode(0, :a)],
           [
-            OptionalParameterNode(0, :b, Location(), Location(), IntegerNode(IntegerBaseFlags::DECIMAL)),
-            OptionalParameterNode(0, :d, Location(), Location(), IntegerNode(IntegerBaseFlags::DECIMAL))
+            OptionalParameterNode(0, :b, Location(), Location(), IntegerNode(IntegerBaseFlags::DECIMAL, 1)),
+            OptionalParameterNode(0, :d, Location(), Location(), IntegerNode(IntegerBaseFlags::DECIMAL, 2))
           ],
           nil,
           [RequiredParameterNode(0, :c), RequiredParameterNode(0, :e)],
@@ -1024,7 +1024,7 @@ module Prism
         Location(),
         nil,
         nil,
-        StatementsNode([IntegerNode(IntegerBaseFlags::DECIMAL)]),
+        StatementsNode([IntegerNode(IntegerBaseFlags::DECIMAL, 42)]),
         [],
         Location(),
         nil,
@@ -1214,7 +1214,7 @@ module Prism
         :foo,
         Location(),
         nil,
-        ParametersNode([], [OptionalParameterNode(0, :a, Location(), Location(), IntegerNode(IntegerBaseFlags::DECIMAL))], RestParameterNode(0, :c, Location(), Location()), [RequiredParameterNode(0, :b)], [], nil, nil),
+        ParametersNode([], [OptionalParameterNode(0, :a, Location(), Location(), IntegerNode(IntegerBaseFlags::DECIMAL, 1))], RestParameterNode(0, :c, Location(), Location()), [RequiredParameterNode(0, :b)], [], nil, nil),
         nil,
         [:a, :b, :c],
         Location(),