diff --git a/emscripten.py b/emscripten.py
index d4e4641c5..3b4597604 100755
--- a/emscripten.py
+++ b/emscripten.py
@@ -480,6 +480,7 @@ def emscript(infile, settings, outfile, libraries=[], compiler_engine=None,
 
 ''' % (sig, i, args, arg_coercions, jsret))
       from tools import shared
+      shared.Settings.copy(settings)
       asm_setup += '\n' + shared.JS.make_invoke(sig) + '\n'
       basic_funcs.append('invoke_%s' % sig)
 
@@ -685,7 +686,7 @@ def main(args, compiler_engine, cache, jcache, relooper, temp_files, DEBUG, DEBU
   for setting in args.settings:
     name, value = setting.strip().split('=', 1)
     settings[name] = json.loads(value)
-  
+
   # libraries
   libraries = args.libraries[0].split(',') if len(args.libraries) > 0 else []
 
diff --git a/tools/shared.py b/tools/shared.py
index 774d95fe6..aecf07993 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -716,6 +716,10 @@ class Settings2(type):
           ret += ['-s', key + '=' + jsoned]
       return ret
 
+    @classmethod
+    def copy(self, values):
+      self.attrs = values
+
     @classmethod
     def apply_opt_level(self, opt_level, noisy=False):
       if opt_level >= 1:
@@ -1443,7 +1447,7 @@ class JS:
     args = ','.join(['a' + str(i) for i in range(1, len(sig))])
     args = 'index' + (',' if args else '') + args
     # C++ exceptions are numbers, and longjmp is a string 'longjmp'
-    return '''function%s(%s) {
+    ret = '''function%s(%s) {
   try {
     %sModule["dynCall_%s"](%s);
   } catch(e) {
@@ -1452,6 +1456,17 @@ class JS:
   }
 }''' % ((' invoke_' + sig) if named else '', args, 'return ' if sig[0] != 'v' else '', sig, args)
 
+    if Settings.DLOPEN_SUPPORT and Settings.ASSERTIONS:
+      # guard against cross-module stack leaks
+      ret = ret.replace('  try {', '''  var preStack = asm.stackSave();
+  try {
+''').replace('  }\n}', '''  } finally {
+    assert(asm.stackSave() == preStack);
+  }
+}''')
+
+    return ret
+
   @staticmethod
   def align(x, by):
     while x % by != 0: x += 1