diff --git a/lib/prism/translation/parser.rb b/lib/prism/translation/parser.rb
index 48a198504b..8df7164688 100644
--- a/lib/prism/translation/parser.rb
+++ b/lib/prism/translation/parser.rb
@@ -135,6 +135,8 @@ module Prism
           Diagnostic.new(:error, :no_anonymous_blockarg, {}, diagnostic_location, [])
         when :argument_no_forwarding_star
           Diagnostic.new(:error, :no_anonymous_restarg, {}, diagnostic_location, [])
+        when :argument_no_forwarding_star_star
+          Diagnostic.new(:error, :no_anonymous_kwrestarg, {}, diagnostic_location, [])
         when :begin_lonely_else
           location = location.copy(length: 4)
           diagnostic_location = build_range(location, offset_cache)
diff --git a/prism/config.yml b/prism/config.yml
index 68b388f2a6..269bfa73ec 100644
--- a/prism/config.yml
+++ b/prism/config.yml
@@ -15,6 +15,7 @@ errors:
   - ARGUMENT_NO_FORWARDING_AMP
   - ARGUMENT_NO_FORWARDING_ELLIPSES
   - ARGUMENT_NO_FORWARDING_STAR
+  - ARGUMENT_NO_FORWARDING_STAR_STAR
   - ARGUMENT_SPLAT_AFTER_ASSOC_SPLAT
   - ARGUMENT_SPLAT_AFTER_SPLAT
   - ARGUMENT_TERM_PAREN
diff --git a/prism/prism.c b/prism/prism.c
index 4e55ac9dbe..955636027e 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -6818,7 +6818,7 @@ pm_parser_scope_forwarding_all_check(pm_parser_t *parser, const pm_token_t * tok
 
 static inline void
 pm_parser_scope_forwarding_keywords_check(pm_parser_t *parser, const pm_token_t * token) {
-    pm_parser_scope_forwarding_param_check(parser, token, PM_SCOPE_PARAMETERS_FORWARDING_KEYWORDS, PM_ERR_EXPECT_EXPRESSION_AFTER_SPLAT_HASH);
+    pm_parser_scope_forwarding_param_check(parser, token, PM_SCOPE_PARAMETERS_FORWARDING_KEYWORDS, PM_ERR_ARGUMENT_NO_FORWARDING_STAR_STAR);
 }
 
 /**
diff --git a/prism/templates/src/diagnostic.c.erb b/prism/templates/src/diagnostic.c.erb
index 1aa261d2c8..2a3ac19930 100644
--- a/prism/templates/src/diagnostic.c.erb
+++ b/prism/templates/src/diagnostic.c.erb
@@ -97,6 +97,7 @@ static const pm_diagnostic_data_t diagnostic_messages[PM_DIAGNOSTIC_ID_MAX] = {
     [PM_ERR_ARGUMENT_NO_FORWARDING_AMP]         = { "unexpected `&` when the parent method is not forwarding", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_ARGUMENT_NO_FORWARDING_ELLIPSES]    = { "unexpected `...` when the parent method is not forwarding", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_ARGUMENT_NO_FORWARDING_STAR]        = { "unexpected `*` when the parent method is not forwarding", PM_ERROR_LEVEL_FATAL },
+    [PM_ERR_ARGUMENT_NO_FORWARDING_STAR_STAR]   = { "unexpected `**` when the parent method is not forwarding", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_ARGUMENT_SPLAT_AFTER_ASSOC_SPLAT]   = { "unexpected `*` splat argument after a `**` keyword splat argument", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_ARGUMENT_SPLAT_AFTER_SPLAT]         = { "unexpected `*` splat argument after a `*` splat argument", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_ARGUMENT_TERM_PAREN]                = { "expected a `)` to close the arguments", PM_ERROR_LEVEL_FATAL },