diff --git a/whalesong/js-assembler/assemble.rkt b/whalesong/js-assembler/assemble.rkt
index 589deee..9f8306c 100644
--- a/whalesong/js-assembler/assemble.rkt
+++ b/whalesong/js-assembler/assemble.rkt
@@ -65,6 +65,7 @@
     (display (assemble-current-interned-constant-closure-table) op)
     
     (display "M.params.currentErrorHandler = fail;\n" op)
+    (display "M.params.currentSuccessHandler = success;\n" op)
     (display  #<<EOF
 for (param in params) {
     if (Object.hasOwnProperty.call(params, param)) {
@@ -79,7 +80,6 @@ EOF
                     (assemble-label (make-Label (BasicBlock-name (first basic-blocks)))))]
           [else
            ;; Otherwise, we want to run under a trampolining context.
-           (display "M.c.push(new RT.CallFrame(function(M){ setTimeout(success, 0); },M.p));\n" op)
            (fprintf op "M.trampoline(~a, ~a); })"
                     (assemble-label (make-Label (BasicBlock-name (first basic-blocks))))
                     (cond [(eq? trampoline-option 'with-preemption)
diff --git a/whalesong/js-assembler/runtime-src/runtime.js b/whalesong/js-assembler/runtime-src/runtime.js
index 572ad42..b431072 100644
--- a/whalesong/js-assembler/runtime-src/runtime.js
+++ b/whalesong/js-assembler/runtime-src/runtime.js
@@ -297,6 +297,7 @@
 	    'currentOutputPort': new StandardOutputPort(),
 	    'currentErrorPort': new StandardErrorPort(),
             'currentInputPort': new StandardInputPort(),
+	    'currentSuccessHandler': function(MACHINE) {},
 	    'currentErrorHandler': function(MACHINE, exn) {
                 MACHINE.params.currentErrorDisplayer(
                     MACHINE,
@@ -752,6 +753,7 @@
 
         that.running = false;
         that.breakScheduled = false;
+        that.params.currentSuccessHandler(that);
         release();
         return;
 
diff --git a/whalesong/tests/test-assemble.rkt b/whalesong/tests/test-assemble.rkt
index 1ee06d1..c8df4e1 100644
--- a/whalesong/tests/test-assemble.rkt
+++ b/whalesong/tests/test-assemble.rkt
@@ -69,7 +69,7 @@
                             (display "var M = new plt.runtime.Machine();\n" op)                           
                             (display "(function() { " op)
                             (display "var myInvoke = " op)
-                            (assemble/write-invoke a-statement op)
+                            (assemble/write-invoke a-statement op 'with-preemption)
                             (display ";" op)
                             (fprintf op 
                                      "return function(succ, fail, params) {