diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/intentions/style/inference/graph/InferenceGraphUtil.kt b/plugins/groovy/src/org/jetbrains/plugins/groovy/intentions/style/inference/graph/InferenceGraphUtil.kt
index 1ec9e3345997..8bcaca8f44d1 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/intentions/style/inference/graph/InferenceGraphUtil.kt
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/intentions/style/inference/graph/InferenceGraphUtil.kt
@@ -168,14 +168,14 @@ private fun PsiType.mapConjuncts(action: (PsiType) -> PsiType): PsiType {
 private class TypeLattice(context: PsiElement) {
   private val manager = context.manager
   private val top = getJavaLangObject(context) as PsiType
-  private val bottom = PsiTypes.nullType() as PsiType
+  private val bottom = PsiTypes.nullType()
 
   fun join(types: Iterable<PsiType>): PsiType = types.fold(bottom) { accum, type ->
-    GenericsUtil.getLeastUpperBound(accum, type, manager) ?: bottom
+    GenericsUtil.getLeastUpperBound(accum, type, manager) ?: top
   }
 
   fun meet(types: Iterable<PsiType>): PsiType = types.fold(top) { accum, type ->
-    GenericsUtil.getGreatestLowerBound(accum, type)
+    GenericsUtil.getGreatestLowerBound(accum, type) ?: bottom
   }
 }