diff --git a/python/src/com/jetbrains/python/psi/types/PyTypeReference.java b/python/src/com/jetbrains/python/psi/types/PyTypeReference.java
index 2f42f2927e06..2e7ba86b9563 100644
--- a/python/src/com/jetbrains/python/psi/types/PyTypeReference.java
+++ b/python/src/com/jetbrains/python/psi/types/PyTypeReference.java
@@ -1,6 +1,7 @@
 package com.jetbrains.python.psi.types;
 
 import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -8,5 +9,5 @@ import org.jetbrains.annotations.Nullable;
  */
 public interface PyTypeReference extends PyType {
   @Nullable
-  PyType resolve(PsiElement context, TypeEvalContext typeEvalContext);
+  PyType resolve(@Nullable PsiElement context, @NotNull TypeEvalContext typeEvalContext);
 }
diff --git a/python/src/com/jetbrains/python/psi/types/PyTypeReferenceImpl.java b/python/src/com/jetbrains/python/psi/types/PyTypeReferenceImpl.java
index e171a26d48bd..1d659bdc4a8a 100644
--- a/python/src/com/jetbrains/python/psi/types/PyTypeReferenceImpl.java
+++ b/python/src/com/jetbrains/python/psi/types/PyTypeReferenceImpl.java
@@ -31,8 +31,9 @@ public abstract class PyTypeReferenceImpl implements PyTypeReference {
     return ArrayUtil.EMPTY_OBJECT_ARRAY;
   }
 
+  @Nullable
   @Override
-  public PyType resolve(@Nullable PsiElement context, TypeEvalContext typeEvalContext) {
+  public PyType resolve(@Nullable PsiElement context, @NotNull TypeEvalContext typeEvalContext) {
     Set<PyTypeReferenceImpl> seen = new HashSet<PyTypeReferenceImpl>();
     seen.add(this);
     PyType resolved;