diff --git a/src/evaluator.js b/src/evaluator.js
index 3daf97da9..198659201 100644
--- a/src/evaluator.js
+++ b/src/evaluator.js
@@ -118,7 +118,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       var self = this;
       var xref = this.xref;
       var handler = this.handler;
-      var uniquePrefix = this.uniquePrefix;
+      var uniquePrefix = this.uniquePrefix || '';
 
       function insertDependency(depList) {
         fnArray.push('dependency');
@@ -235,7 +235,6 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           }, handler, xref, resources, image, inline);
       }
 
-      uniquePrefix = uniquePrefix || '';
       if (!queue.argsArray) {
         queue.argsArray = [];
       }
diff --git a/test/unit/obj_spec.js b/test/unit/obj_spec.js
index 02e268fd4..7049e769f 100644
--- a/test/unit/obj_spec.js
+++ b/test/unit/obj_spec.js
@@ -127,5 +127,23 @@ describe('obj', function() {
       expect(ref.gen).toEqual(storedGen);
     });
   });
+
+  describe('RefSet', function() {
+    it('should have a stored value', function() {
+      var ref = new Ref(4, 2);
+      var refset = new RefSet();
+      refset.put(ref);
+      expect(refset.has(ref)).toBeTruthy();
+    });
+    it('should not have an unknown value', function() {
+      var ref = new Ref(4, 2);
+      var refset = new RefSet();
+      expect(refset.has(ref)).toBeFalsy();
+
+      refset.put(ref);
+      var anotherRef = new Ref(2, 4);
+      expect(refset.has(anotherRef)).toBeFalsy();
+    });
+  });
 });