diff --git a/blocks/procedures.js b/blocks/procedures.js
index c309a2516..4a89582b4 100644
--- a/blocks/procedures.js
+++ b/blocks/procedures.js
@@ -836,7 +836,7 @@ Blockly.Blocks['procedures_callnoreturn'] = {
       var name = this.getProcedureCall();
       var def = Blockly.Procedures.getDefinition(name, this.workspace);
       if (def && (def.type != this.defType_ ||
-          JSON.stringify(def.arguments_) != JSON.stringify(this.arguments_))) {
+          JSON.stringify(def.getVars()) != JSON.stringify(this.arguments_))) {
         // The signatures don't match.
         def = null;
       }