diff --git a/broken-fact.rkt b/broken-fact.rkt
index d2ca022..e745c43 100644
--- a/broken-fact.rkt
+++ b/broken-fact.rkt
@@ -5,5 +5,6 @@
       "one"
       (* x (f (sub1 x)))))
 
+(f 0)
 (list (f 3)
       (f 4))
diff --git a/js-assembler/assemble-helpers.rkt b/js-assembler/assemble-helpers.rkt
index cef6ec9..c84b621 100644
--- a/js-assembler/assemble-helpers.rkt
+++ b/js-assembler/assemble-helpers.rkt
@@ -137,9 +137,9 @@
                (format "RUNTIME.makePath(~s)"
                        (path->string val))]
               [(vector? val)
-               (format "RUNTIME.makeVector(~s)"
+               (format "RUNTIME.makeVector(~a)"
                        (string-join (for/list ([elt (vector->list val)])
-                                        (loop elt))
+                                       (loop elt))
                                     ","))]
               [(box? val)
                (format "RUNTIME.makeBox(~s)"
diff --git a/js-assembler/package.rkt b/js-assembler/package.rkt
index 05c228e..6b2968c 100644
--- a/js-assembler/package.rkt
+++ b/js-assembler/package.rkt
@@ -435,12 +435,14 @@ var invokeMainModule = function() {
                                  appNames = contMarkSet.ref(plt.runtime.getTracedAppKey(MACHINE));
                                  while (plt.baselib.lists.isPair(appNames)) {
                                      appName = appNames.first;
-                                     console.log(appName);
                                      MACHINE.params.currentErrorDisplayer(
                                         MACHINE,
                                         $('<div/>').text('  at ' + appName.elts[0] +
                                                          ', line ' + appName.elts[2] +
                                                          ', column ' + appName.elts[3])
+                                                   .addClass('stacktrace')
+                                                   .css('margin-left', '10px')
+                                                   .css('whitespace', 'pre')
                                                    .css('color', 'red'));
                                      appNames = appNames.rest;
                                  }