diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index 46bd33d1db..7aee20c9de 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -204,8 +204,8 @@ module Prism
           LengthCounter.new(source, encoding)
         end
 
-      @cache = {}
-      @offsets = []
+      @cache = {} #: Hash[Integer, Integer]
+      @offsets = [] #: Array[Integer]
     end
 
     # Retrieve the code units offset from the given byte offset.
diff --git a/lib/prism/parse_result/errors.rb b/lib/prism/parse_result/errors.rb
index 847a8442fe..eb4f317248 100644
--- a/lib/prism/parse_result/errors.rb
+++ b/lib/prism/parse_result/errors.rb
@@ -17,7 +17,7 @@ module Prism
 
       # Formats the errors in a human-readable way and return them as a string.
       def format
-        error_lines = {}
+        error_lines = {} #: Hash[Integer, Array[ParseError]]
         parse_result.errors.each do |error|
           location = error.location
           (location.start_line..location.end_line).each do |line|
diff --git a/lib/prism/relocation.rb b/lib/prism/relocation.rb
index ad914396f6..163d2012c5 100644
--- a/lib/prism/relocation.rb
+++ b/lib/prism/relocation.rb
@@ -465,7 +465,7 @@ module Prism
         while (node = queue.shift)
           @entries[node.node_id].each do |field_name, entry|
             value = node.public_send(field_name)
-            values = {}
+            values = {} #: Hash[Symbol, untyped]
 
             fields.each_value do |field|
               values.merge!(field.fields(value))
diff --git a/prism/templates/lib/prism/node.rb.erb b/prism/templates/lib/prism/node.rb.erb
index 72245cd30d..e4ca185719 100644
--- a/prism/templates/lib/prism/node.rb.erb
+++ b/prism/templates/lib/prism/node.rb.erb
@@ -182,7 +182,7 @@ module Prism
     # bytes, as opposed to characters or code units.
     def tunnel(line, column)
       queue = [self] #: Array[Prism::node]
-      result = []
+      result = [] #: Array[Prism::node]
 
       while (node = queue.shift)
         result << node