diff --git a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/lookup/TypeVariableBinding.java b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/lookup/TypeVariableBinding.java
index e463960..4b0fa80 100644
--- a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/lookup/TypeVariableBinding.java
+++ b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/lookup/TypeVariableBinding.java
@@ -320,7 +320,7 @@
 				for (int i = 0, l = this.superInterfaces.length; i < l; i++)
 					this.typeBits |= this.superInterfaces[i].typeBits;
 		}
-		return (this.typeBits & bit) != 0;
+		return ((this.typeBits != -1) && (this.typeBits & bit) != 0);
 	}
 
 	/**