diff --git a/lib/imbecile/generator.rb b/lib/imbecile/generator.rb
index 081b32c..c8bf164 100644
--- a/lib/imbecile/generator.rb
+++ b/lib/imbecile/generator.rb
@@ -9,6 +9,19 @@ module Imbecile
     end
 
     def generate(output_file)
+      token_names = @grammar.tokens.each_with_object({}) do |token, token_names|
+        if token_names.include?(token.name)
+          raise Error.new("Duplicate token name #{token.name}")
+        end
+        token_names[token.name] = token
+      end
+      rule_names = @grammar.rules.each_with_object({}) do |rule, rule_names|
+        if token_names.include?(rule.name)
+          raise Error.new("Rule name collides with token name #{rule.name}")
+        end
+        rule_names[rule.name] ||= []
+        rule_names[rule.name] << rule
+      end
       lexer_dfa = LexerDFA.new(@grammar.tokens)
       classname = @grammar.classname || output_file.sub(%r{[^a-zA-Z0-9].*}, "").capitalize
       erb = ERB.new(File.read(File.join(File.dirname(File.expand_path(__FILE__)), "../../assets/parser.d.erb")), nil, "<>")
diff --git a/lib/imbecile/grammar.rb b/lib/imbecile/grammar.rb
index d9c1dfa..2a0375b 100644
--- a/lib/imbecile/grammar.rb
+++ b/lib/imbecile/grammar.rb
@@ -16,7 +16,6 @@ module Imbecile
     def initialize(input)
       @tokens = []
       @rules = []
-      @token_names = Set.new
       input = input.gsub("\r\n", "\n")
       while !input.empty?
         consume(input)
@@ -42,11 +41,7 @@ module Imbecile
         unless name =~ /^[a-zA-Z_][a-zA-Z_0-9]*$/
           raise Error.new("Invalid token name #{name}")
         end
-        if @token_names.include?(name)
-          raise Error.new("Duplicate token name #{name}")
-        end
         @tokens << Token.new(name, pattern, @tokens.size)
-        @token_names << name
       elsif input.slice!(/\Adrop\s+(\S+)\n/)
         pattern = $1
         @tokens << Token.new(nil, pattern, @tokens.size)