diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/annotator/GroovyAnnotator.java b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/annotator/GroovyAnnotator.java
index 8ff91f1cff32..208ef178f185 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/annotator/GroovyAnnotator.java
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/annotator/GroovyAnnotator.java
@@ -1964,8 +1964,13 @@ public class GroovyAnnotator extends GroovyElementVisitor {
   }
 
   private void doCheckDuplicateMethod(@NotNull GrMethod method, @NotNull PsiClass clazz) {
-    MethodSignature signature = GrClassImplUtil.getDuplicatedMethods(clazz).get(method);
-    if (signature == null) return;
+    Set<MethodSignature> duplicatedSignatures = GrClassImplUtil.getDuplicatedSignatures(clazz);
+    if (duplicatedSignatures.isEmpty()) return; // optimization
+
+    PsiSubstitutor substitutor = JavaPsiFacade.getElementFactory(method.getProject()).createRawSubstitutor(method);
+    MethodSignature signature = method.getSignature(substitutor);
+    if (!duplicatedSignatures.contains(signature)) return;
+
     String signaturePresentation = GroovyPresentationUtil.getSignaturePresentation(signature);
     GrMethod original = method instanceof GrReflectedMethod ? ((GrReflectedMethod)method).getBaseMethod() : method;
     myHolder.createErrorAnnotation(
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/util/GrClassImplUtil.java b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/util/GrClassImplUtil.java
index e878aca2e44c..3ac99f81dc3b 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/util/GrClassImplUtil.java
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/util/GrClassImplUtil.java
@@ -619,23 +619,19 @@ public class GrClassImplUtil {
   }
 
   @NotNull
-  public static Map<PsiMethod, MethodSignature> getDuplicatedMethods(@NotNull PsiClass clazz) {
+  public static Set<MethodSignature> getDuplicatedSignatures(@NotNull PsiClass clazz) {
     return CachedValuesManager.getCachedValue(clazz, () -> {
       PsiElementFactory factory = JavaPsiFacade.getInstance(clazz.getProject()).getElementFactory();
-
       MostlySingularMultiMap<MethodSignature, PsiMethod> signatures = MostlySingularMultiMap.newMap();
       for (PsiMethod method : clazz.getMethods()) {
         MethodSignature signature = method.getSignature(factory.createRawSubstitutor(method));
         signatures.add(signature, method);
       }
 
-      Map<PsiMethod, MethodSignature> result = ContainerUtil.newHashMap();
+      Set<MethodSignature> result = ContainerUtil.newHashSet();
       for (MethodSignature signature : signatures.keySet()) {
         if (signatures.valuesForKey(signature) > 1) {
-          signatures.processForKey(signature, m -> {
-            result.put(m, signature);
-            return true;
-          });
+          result.add(signature);
         }
       }