1 files changed, 6 insertions, 0 deletions
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 79b5d70f4..66ada79f2 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -1183,6 +1183,12 @@ Parser<ParseHandler>::tryDeclareVar(HandlePropertyName name, DeclarationKind kin
                     *redeclaredKind = Some(declaredKind);
                     return true;
                 }
+            } else if (kind == DeclarationKind::VarForAnnexBLexicalFunction) {
+                MOZ_ASSERT(DeclarationKindIsParameter(declaredKind));
+
+                // Annex B.3.3.1 disallows redeclaring parameter names.
+                *redeclaredKind = Some(declaredKind);
+                return true;
             }
         } else {
             if (!scope->addDeclaredName(pc, p, name, kind))