diff --git a/java/java-psi-api/src/com/intellij/psi/PsiClassType.java b/java/java-psi-api/src/com/intellij/psi/PsiClassType.java
index f97060a4ad6e..7c80c1112479 100644
--- a/java/java-psi-api/src/com/intellij/psi/PsiClassType.java
+++ b/java/java-psi-api/src/com/intellij/psi/PsiClassType.java
@@ -214,7 +214,7 @@ public abstract class PsiClassType extends PsiType {
 
 
   @Override
-  public <A> A accept(PsiTypeVisitor<A> visitor) {
+  public <A> A accept(@NotNull PsiTypeVisitor<A> visitor) {
     return visitor.visitClassType(this);
   }
 
@@ -226,7 +226,8 @@ public abstract class PsiClassType extends PsiType {
    * @param languageLevel level to obtain class type with
    * @return type with requested language level
    */
-  public abstract PsiClassType setLanguageLevel(final LanguageLevel languageLevel);
+  @NotNull
+  public abstract PsiClassType setLanguageLevel(@NotNull LanguageLevel languageLevel);
 
   /**
    * Represents the result of resolving a reference to a Java class.
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiClassReferenceType.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiClassReferenceType.java
index 8845368cfa5f..9f1aeb5ad548 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiClassReferenceType.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiClassReferenceType.java
@@ -78,8 +78,9 @@ public class PsiClassReferenceType extends PsiClassType {
     return PsiUtil.getLanguageLevel(myReference);
   }
 
+  @NotNull
   @Override
-  public PsiClassType setLanguageLevel(final LanguageLevel languageLevel) {
+  public PsiClassType setLanguageLevel(@NotNull final LanguageLevel languageLevel) {
     if (languageLevel.equals(myLanguageLevel)) return this;
     return new PsiClassReferenceType(myReference,languageLevel,getAnnotations());
   }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiImmediateClassType.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiImmediateClassType.java
index bba0cfe69f22..0df5a110b042 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiImmediateClassType.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/PsiImmediateClassType.java
@@ -261,8 +261,9 @@ public class PsiImmediateClassType extends PsiClassType {
     return PsiUtil.getLanguageLevel(myClass);
   }
 
+  @NotNull
   @Override
-  public PsiClassType setLanguageLevel(final LanguageLevel languageLevel) {
+  public PsiClassType setLanguageLevel(@NotNull final LanguageLevel languageLevel) {
     if (languageLevel.equals(myLanguageLevel)) return this;
     return new PsiImmediateClassType(myClass, mySubstitutor, languageLevel,getAnnotations());
   }
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClassReferenceType.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClassReferenceType.java
index a77ed5300cb8..b471114d9cea 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClassReferenceType.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClassReferenceType.java
@@ -147,7 +147,8 @@ public class GrClassReferenceType extends PsiClassType {
     return myLanguageLevel;
   }
 
-  public PsiClassType setLanguageLevel(final LanguageLevel languageLevel) {
+  @NotNull
+  public PsiClassType setLanguageLevel(@NotNull final LanguageLevel languageLevel) {
     return new GrClassReferenceType(myReferenceElement,languageLevel);
   }
 }
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClosureType.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClosureType.java
index 8badf06ce17c..7c00c765a3a3 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClosureType.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrClosureType.java
@@ -143,7 +143,8 @@ public class GrClosureType extends GrLiteralClassType {
     return text.equals(GroovyCommonClassNames.GROOVY_LANG_CLOSURE);
   }
 
-  public PsiClassType setLanguageLevel(final LanguageLevel languageLevel) {
+  @NotNull
+  public PsiClassType setLanguageLevel(@NotNull final LanguageLevel languageLevel) {
     final GrClosureType result = create(mySignature, myScope, myFacade, languageLevel, true);
     result.myTypeArgs = this.myTypeArgs;
     return result;
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrMapType.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrMapType.java
index 39e811466cf8..d171b26f336f 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrMapType.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrMapType.java
@@ -188,7 +188,8 @@ public class GrMapType extends GrLiteralClassType {
     return true;
   }
 
-  public PsiClassType setLanguageLevel(final LanguageLevel languageLevel) {
+  @NotNull
+  public PsiClassType setLanguageLevel(@NotNull final LanguageLevel languageLevel) {
     return new GrMapType(myFacade, getResolveScope(), myStringEntries, myOtherEntries, languageLevel);
   }
 
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrRangeType.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrRangeType.java
index 1937c0c05f4d..bdd93682e691 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrRangeType.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrRangeType.java
@@ -77,8 +77,9 @@ public class GrRangeType extends GrLiteralClassType {
     return PsiType.EMPTY_ARRAY;
   }
 
+  @NotNull
   @Override
-  public PsiClassType setLanguageLevel(LanguageLevel languageLevel) {
+  public PsiClassType setLanguageLevel(@NotNull LanguageLevel languageLevel) {
     return new GrRangeType(languageLevel, myScope, myFacade, myLeft, myRight);
   }
 
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrTupleType.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrTupleType.java
index 0f1d9decda71..0be4a6698d82 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrTupleType.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrTupleType.java
@@ -90,7 +90,8 @@ public class GrTupleType extends GrLiteralClassType {
     return true;
   }
 
-  public PsiClassType setLanguageLevel(final LanguageLevel languageLevel) {
+  @NotNull
+  public PsiClassType setLanguageLevel(@NotNull final LanguageLevel languageLevel) {
     return new GrTupleType(myComponentTypes, myFacade, myScope,languageLevel);
   }