diff --git a/test/default/pre.js.inc b/test/default/pre.js.inc
index 130c1371..8b8d589a 100755
--- a/test/default/pre.js.inc
+++ b/test/default/pre.js.inc
@@ -5,12 +5,14 @@ try {
     this['Module'] = Module = {};
 }
 if (typeof process === 'object') {
-    Module['preRun'] = Module['preRun'] || [];
-    Module['preRun'].push(function() {
-        FS.init();
-        FS.mkdir('/test-data');
-        FS.mount(NODEFS,  { root: '.' }, '/test-data');
-    });
+    if (typeof(FS) === 'object') {
+        Module['preRun'] = Module['preRun'] || [];
+        Module['preRun'].push(function() {
+            FS.init();
+            FS.mkdir('/test-data');
+            FS.mount(NODEFS,  { root: '.' }, '/test-data');
+        });
+    }
 } else {
     Module['print'] = function(x) {
         var event = new Event('test-output');