diff --git a/java/java-psi-api/src/com/intellij/psi/util/TypeConversionUtil.java b/java/java-psi-api/src/com/intellij/psi/util/TypeConversionUtil.java
index 5c7044ac58e5..dbfc77322661 100644
--- a/java/java-psi-api/src/com/intellij/psi/util/TypeConversionUtil.java
+++ b/java/java-psi-api/src/com/intellij/psi/util/TypeConversionUtil.java
@@ -1129,6 +1129,7 @@ public class TypeConversionUtil {
                                                    PsiClass base,
                                                    Set<PsiClass> set,
                                                    PsiManager manager) {
+    assert candidateSubstitutor.isValid();
     for (final PsiClassType type : types) {
       final PsiType substitutedType = candidateSubstitutor.substitute(type);
       //if (!(substitutedType instanceof PsiClassType)) return null;