diff --git a/lib/feature_extractor.js b/lib/feature_extractor.js
index c4bef4f5..e13c204e 100644
--- a/lib/feature_extractor.js
+++ b/lib/feature_extractor.js
@@ -115,7 +115,7 @@ function nodeToString(node) {
 		}		
 		return INFER + node.definition().id + "-" + node.name;		
 	} else if (node instanceof AST_Constant){
-		return GIVEN + String(node.value).slice(0,64);
+		return GIVEN + "!" + nodeType(node) + "!" + String(node.value).slice(0,64);
 	} else if (node instanceof AST_Sub){
 		//x[1], x -> expression, 1 -> property
 		return nodeToString(node.expression) + "[]";