diff --git a/src/engine/execute.js b/src/engine/execute.js
index aa413a76b..9317add96 100644
--- a/src/engine/execute.js
+++ b/src/engine/execute.js
@@ -13,7 +13,7 @@ var execute = function (sequencer, thread) {
     var currentBlockId = thread.peekStack();
     var currentStackFrame = thread.peekStackFrame();
 
-    var opcode = runtime.blocks.getOpcode(currentBlockId);
+    var opcode = target.blocks.getOpcode(currentBlockId);
 
     if (!opcode) {
         console.warn('Could not get opcode for block: ' + currentBlockId);