diff --git a/java/java-impl/src/com/intellij/slicer/JavaDfaSliceValueFilter.java b/java/java-impl/src/com/intellij/slicer/JavaDfaSliceValueFilter.java
index b1495dea325f..c2ea96663016 100644
--- a/java/java-impl/src/com/intellij/slicer/JavaDfaSliceValueFilter.java
+++ b/java/java-impl/src/com/intellij/slicer/JavaDfaSliceValueFilter.java
@@ -20,7 +20,7 @@ public class JavaDfaSliceValueFilter implements SliceValueFilter {
   }
 
   @Override
-  public boolean allowed(PsiElement element) {
+  public boolean allowed(@NotNull PsiElement element) {
     if (myDfType instanceof DfConstantType && element instanceof PsiLiteralValue) {
       Object constValue = ((DfConstantType<?>)myDfType).getValue();
       if (!(constValue instanceof PsiElement)) {
@@ -34,7 +34,7 @@ public class JavaDfaSliceValueFilter implements SliceValueFilter {
   }
 
   @Override
-  public String toString() {
+  public @NotNull String toString() {
     return myDfType.toString();
   }
 }
diff --git a/platform/lang-impl/src/com/intellij/slicer/SliceValueFilter.java b/platform/lang-impl/src/com/intellij/slicer/SliceValueFilter.java
index 2eb4405a6359..6f4d80408f74 100644
--- a/platform/lang-impl/src/com/intellij/slicer/SliceValueFilter.java
+++ b/platform/lang-impl/src/com/intellij/slicer/SliceValueFilter.java
@@ -3,16 +3,17 @@ package com.intellij.slicer;
 
 import com.intellij.psi.PsiElement;
 import org.jetbrains.annotations.Nls;
+import org.jetbrains.annotations.NotNull;
 
 public interface SliceValueFilter {
   /**
    * @param element to test
    * @return true if this element passes the filter
    */
-  boolean allowed(PsiElement element);
+  boolean allowed(@NotNull PsiElement element);
   
   /**
    * @return String representation
    */
-  @Nls String toString();
+  @NotNull @Nls String toString();
 }