diff --git a/lib/prism/translation/parser.rb b/lib/prism/translation/parser.rb
index 6a2a9bbf24..48a198504b 100644
--- a/lib/prism/translation/parser.rb
+++ b/lib/prism/translation/parser.rb
@@ -124,7 +124,7 @@ module Prism
         when :argument_block_multi
           Diagnostic.new(:error, :block_and_blockarg, {}, diagnostic_location, [])
         when :argument_formal_constant
-          Diagnostic.new(:error, :formal_argument, {}, diagnostic_location, [])
+          Diagnostic.new(:error, :argument_const, {}, diagnostic_location, [])
         when :argument_formal_class
           Diagnostic.new(:error, :argument_cvar, {}, diagnostic_location, [])
         when :argument_formal_global