diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PropertyStubType.java b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PropertyStubType.java
index 32fe80a2f039..4a261db6ff12 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PropertyStubType.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PropertyStubType.java
@@ -18,6 +18,7 @@ package com.jetbrains.python.psi.impl.stubs;
 import com.intellij.psi.stubs.StubInputStream;
 import com.jetbrains.python.psi.PyTargetExpression;
 import com.jetbrains.python.psi.stubs.PropertyStubStorage;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.IOException;
@@ -26,12 +27,12 @@ import java.io.IOException;
 public final class PropertyStubType extends CustomTargetExpressionStubType<PropertyStubStorage> {
   @Nullable
   @Override
-  public PropertyStubStorage createStub(PyTargetExpression psi) {
+  public PropertyStubStorage createStub(@NotNull PyTargetExpression psi) {
     return PropertyStubStorage.fromCall(psi.findAssignedValue());
   }
 
   @Override
-  public PropertyStubStorage deserializeStub(StubInputStream stream) throws IOException {
+  public PropertyStubStorage deserializeStub(@NotNull StubInputStream stream) throws IOException {
     return PropertyStubStorage.deserialize(stream);
   }
 }
diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingAliasStubType.java b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingAliasStubType.java
index 9430c857e753..b44e4863db55 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingAliasStubType.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingAliasStubType.java
@@ -55,7 +55,7 @@ public final class PyTypingAliasStubType extends CustomTargetExpressionStubType<
 
   @Nullable
   @Override
-  public PyTypingAliasStub createStub(PyTargetExpression psi) {
+  public PyTypingAliasStub createStub(@NotNull PyTargetExpression psi) {
     final PyExpression value = getAssignedValueIfTypeAliasLike(psi, true);
     return value != null ? new PyTypingTypeAliasStubImpl(value.getText()) : null;
   }
@@ -155,7 +155,7 @@ public final class PyTypingAliasStubType extends CustomTargetExpressionStubType<
 
   @Nullable
   @Override
-  public PyTypingAliasStub deserializeStub(StubInputStream stream) throws IOException {
+  public PyTypingAliasStub deserializeStub(@NotNull StubInputStream stream) throws IOException {
     String ref = stream.readNameString();
     return ref != null ? new PyTypingTypeAliasStubImpl(ref) : null;
   }
diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingTypeAliasStubImpl.java b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingTypeAliasStubImpl.java
index c00733a89999..4daea88514a9 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingTypeAliasStubImpl.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/stubs/PyTypingTypeAliasStubImpl.java
@@ -46,7 +46,7 @@ public class PyTypingTypeAliasStubImpl implements PyTypingAliasStub {
   }
 
   @Override
-  public void serialize(StubOutputStream stream) throws IOException {
+  public void serialize(@NotNull StubOutputStream stream) throws IOException {
     stream.writeName(myText);
   }
 
diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PropertyStubStorage.java b/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PropertyStubStorage.java
index 6ec1a28f0007..6d3e82f72024 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PropertyStubStorage.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PropertyStubStorage.java
@@ -50,7 +50,7 @@ public class PropertyStubStorage extends PropertyBunch<String> implements Custom
   }
 
   @Override
-  public void serialize(StubOutputStream stream) throws IOException {
+  public void serialize(@NotNull StubOutputStream stream) throws IOException {
     writeOne(myGetter, stream);
     writeOne(mySetter, stream);
     writeOne(myDeleter, stream);