diff --git a/prism/extension.c b/prism/extension.c
index b7c59e514e..416e682f76 100644
--- a/prism/extension.c
+++ b/prism/extension.c
@@ -987,12 +987,12 @@ inspect_node(VALUE self, VALUE source) {
 
 /**
  * call-seq:
- *   Debug::format_errors(source) -> String
+ *   Debug::format_errors(source, colorize) -> String
  *
  * Format the errors that are found when parsing the given source string.
  */
 static VALUE
-format_errors(VALUE self, VALUE source) {
+format_errors(VALUE self, VALUE source, VALUE colorize) {
     pm_string_t input;
     input_load_string(&input, source);
 
@@ -1002,7 +1002,7 @@ format_errors(VALUE self, VALUE source) {
     pm_node_t *node = pm_parse(&parser);
     pm_buffer_t buffer = { 0 };
 
-    pm_parser_errors_format(&parser, &buffer, true);
+    pm_parser_errors_format(&parser, &buffer, RTEST(colorize));
 
     rb_encoding *encoding = rb_enc_find(parser.encoding->name);
     VALUE result = rb_enc_str_new(pm_buffer_value(&buffer), pm_buffer_length(&buffer), encoding);
@@ -1093,7 +1093,7 @@ Init_prism(void) {
     rb_define_singleton_method(rb_cPrismDebug, "memsize", memsize, 1);
     rb_define_singleton_method(rb_cPrismDebug, "profile_file", profile_file, 1);
     rb_define_singleton_method(rb_cPrismDebug, "inspect_node", inspect_node, 1);
-    rb_define_singleton_method(rb_cPrismDebug, "format_errors", format_errors, 1);
+    rb_define_singleton_method(rb_cPrismDebug, "format_errors", format_errors, 2);
 
     // Next, initialize the other APIs.
     Init_prism_api_node();
diff --git a/prism/prism.c b/prism/prism.c
index a078100e3b..4a6797896b 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -17873,7 +17873,7 @@ pm_parser_errors_format_sort(const pm_list_t *error_list, const pm_newline_list_
         if (start.line == end.line) {
             column_end = (uint32_t) end.column;
         } else {
-            column_end = (uint32_t) (newline_list->offsets[start.line + 1] - newline_list->offsets[start.line] - 1);
+            column_end = (uint32_t) (newline_list->offsets[start.line] - newline_list->offsets[start.line - 1] - 1);
         }
 
         // Ensure we have at least one column of error.
@@ -17892,16 +17892,16 @@ pm_parser_errors_format_sort(const pm_list_t *error_list, const pm_newline_list_
 
 static inline void
 pm_parser_errors_format_line(const pm_parser_t *parser, const pm_newline_list_t *newline_list, const char *number_prefix, size_t line, pm_buffer_t *buffer) {
-    const uint8_t *start = &parser->start[newline_list->offsets[line]];
+    const uint8_t *start = &parser->start[newline_list->offsets[line - 1]];
     const uint8_t *end;
 
-    if (line + 1 >= newline_list->size) {
+    if (line >= newline_list->size) {
         end = parser->end;
     } else {
-        end = &parser->start[newline_list->offsets[line + 1]];
+        end = &parser->start[newline_list->offsets[line]];
     }
 
-    pm_buffer_append_format(buffer, number_prefix, (uint32_t) (line + 1));
+    pm_buffer_append_format(buffer, number_prefix, (uint32_t) line);
     pm_buffer_append_string(buffer, (const char *) start, (size_t) (end - start));
 
     if (end == parser->end && end[-1] != '\n') {
@@ -17926,7 +17926,7 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
     // blank lines based on the maximum number of digits in the line numbers
     // that are going to be displayed.
     pm_error_format_t error_format;
-    size_t max_line_number = errors[error_list->size - 1].line + 1;
+    size_t max_line_number = errors[error_list->size - 1].line;
 
     if (max_line_number < 10) {
         if (colorize) {
@@ -18008,7 +18008,7 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
     // the source before the error to give some context. We'll be careful not to
     // display the same line twice in case the errors are close enough in the
     // source.
-    uint32_t last_line = (uint32_t) -1;
+    uint32_t last_line = 0;
     const pm_encoding_t *encoding = parser->encoding;
 
     for (size_t index = 0; index < error_list->size; index++) {
@@ -18054,7 +18054,7 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
         pm_buffer_append_string(buffer, error_format.blank_prefix, error_format.blank_prefix_length);
 
         size_t column = 0;
-        const uint8_t *start = &parser->start[newline_list->offsets[error->line]];
+        const uint8_t *start = &parser->start[newline_list->offsets[error->line - 1]];
 
         while (column < error->column_end) {
             if (column < error->column_start) {
@@ -18078,7 +18078,7 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
         // Here we determine how many lines of padding to display after the
         // error, depending on where the next error is in source.
         last_line = error->line;
-        size_t next_line = (index == error_list->size - 1) ? newline_list->size - 1 : errors[index + 1].line;
+        size_t next_line = (index == error_list->size - 1) ? newline_list->size : errors[index + 1].line;
 
         if (next_line - last_line > 1) {
             pm_buffer_append_string(buffer, "  ", 2);
diff --git a/prism/templates/src/prettyprint.c.erb b/prism/templates/src/prettyprint.c.erb
index 02b89758b8..605795b64a 100644
--- a/prism/templates/src/prettyprint.c.erb
+++ b/prism/templates/src/prettyprint.c.erb
@@ -40,7 +40,7 @@ static inline void
 prettyprint_location(pm_buffer_t *output_buffer, const pm_parser_t *parser, const pm_location_t *location) {
     pm_line_column_t start = pm_newline_list_line_column(&parser->newline_list, location->start);
     pm_line_column_t end = pm_newline_list_line_column(&parser->newline_list, location->end);
-    pm_buffer_append_format(output_buffer, "(%lu,%lu)-(%lu,%lu)", (unsigned long) (start.line + 1), (unsigned long) start.column, (unsigned long) (end.line + 1), (unsigned long) end.column);
+    pm_buffer_append_format(output_buffer, "(%lu,%lu)-(%lu,%lu)", (unsigned long) start.line, (unsigned long) start.column, (unsigned long) end.line, (unsigned long) end.column);
 }
 
 static inline void
diff --git a/prism/util/pm_newline_list.c b/prism/util/pm_newline_list.c
index 32a4a050fe..724d840dd2 100644
--- a/prism/util/pm_newline_list.c
+++ b/prism/util/pm_newline_list.c
@@ -62,7 +62,7 @@ pm_newline_list_line_column(const pm_newline_list_t *list, const uint8_t *cursor
         size_t mid = left + (right - left) / 2;
 
         if (list->offsets[mid] == offset) {
-            return ((pm_line_column_t) { mid, 0 });
+            return ((pm_line_column_t) { mid + 1, 0 });
         }
 
         if (list->offsets[mid] < offset) {
@@ -72,7 +72,7 @@ pm_newline_list_line_column(const pm_newline_list_t *list, const uint8_t *cursor
         }
     }
 
-    return ((pm_line_column_t) { left - 1, offset - list->offsets[left - 1] });
+    return ((pm_line_column_t) { left, offset - list->offsets[left - 1] });
 }
 
 /**
diff --git a/test/prism/format_errors_test.rb b/test/prism/format_errors_test.rb
new file mode 100644
index 0000000000..62b24723b8
--- /dev/null
+++ b/test/prism/format_errors_test.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+return if Prism::BACKEND == :FFI
+
+require_relative "test_helper"
+
+module Prism
+  class FormatErrorsTest < TestCase
+    def test_format_errors
+      assert_equal <<~ERROR, Debug.format_errors("<>", false)
+        > 1 | <>
+            | ^ cannot parse the expression
+            |  ^ cannot parse the expression
+      ERROR
+    end
+  end
+end