diff --git a/platform/lang-api/src/com/intellij/codeInsight/lookup/LookupElementBuilder.java b/platform/lang-api/src/com/intellij/codeInsight/lookup/LookupElementBuilder.java
index 36fe492e78f9..8a028395c6ae 100644
--- a/platform/lang-api/src/com/intellij/codeInsight/lookup/LookupElementBuilder.java
+++ b/platform/lang-api/src/com/intellij/codeInsight/lookup/LookupElementBuilder.java
@@ -41,10 +41,10 @@ public final class LookupElementBuilder extends LookupElement {
   @Nullable private final LookupElementPresentation myHardcodedPresentation;
   @NotNull private final Set<String> myAllLookupStrings;
 
-  private LookupElementBuilder(String lookupString, Object object, @Nullable InsertHandler<LookupElement> insertHandler,
+  private LookupElementBuilder(@NotNull String lookupString, @NotNull Object object, @Nullable InsertHandler<LookupElement> insertHandler,
                                @Nullable LookupElementRenderer<LookupElement> renderer,
                                @Nullable LookupElementPresentation hardcodedPresentation,
-                               Set<String> allLookupStrings,
+                               @NotNull Set<String> allLookupStrings,
                                boolean caseSensitive) {
     myLookupString = lookupString;
     myObject = object;