diff --git a/lib/expressions.js b/lib/expressions.js
index 8ce0804..200ae53 100644
--- a/lib/expressions.js
+++ b/lib/expressions.js
@@ -409,20 +409,20 @@ FnExpression.prototype._lookupParent = function(context) {
   // Lookup function in the model
   var segments = this.parentSegments;
   var parent = (segments) ? lookup(segments, context.controller.model.data) : undefined;
-  if (parent && parent[this.lastSegment]) return parent;
-  // Lookup function on current controller
+  if (parent && typeof parent[this.lastSegment] == 'function') return parent;
+  // Otherwise lookup function on current controller
   var controller = context.controller;
   parent = (segments) ? lookup(segments, controller) : controller;
-  if (parent && parent[this.lastSegment]) return parent;
+  if (parent && typeof parent[this.lastSegment] == 'function') return parent;
   // Otherwise lookup function on page
   var page = controller.page;
   if (controller !== page) {
     parent = (segments) ? lookup(segments, page) : page;
-    if (parent && parent[this.lastSegment]) return parent;
+    if (parent && typeof parent[this.lastSegment] == 'function') return parent;
   }
   // Otherwise lookup function on global
   parent = (segments) ? lookup(segments, global) : global;
-  if (parent && parent[this.lastSegment]) return parent;
+  if (parent && typeof parent[this.lastSegment] == 'function') return parent;
   // Throw if not found
   throw new Error('Function not found for: ' + this.segments.join('.'));
 };