diff --git a/lib/ansible/plugins/action/assemble.py b/lib/ansible/plugins/action/assemble.py
index e02f866395..3269c6e01e 100644
--- a/lib/ansible/plugins/action/assemble.py
+++ b/lib/ansible/plugins/action/assemble.py
@@ -110,17 +110,13 @@ class ActionModule(ActionBase):
         dest = self._remote_expand_user(dest, tmp)
         remote_checksum = self._remote_checksum(tmp, dest, all_vars=task_vars)
 
+        diff = {}
         if path_checksum != remote_checksum:
             resultant = file(path).read()
-            # FIXME: diff needs to be moved somewhere else
-            #if self.runner.diff:
-            #    dest_result = self._execute_module(module_name='slurp', module_args=dict(path=dest), task_vars=task_vars, tmp=tmp, persist_files=True)
-            #    if 'content' in dest_result:
-            #        dest_contents = dest_result['content']
-            #        if dest_result['encoding'] == 'base64':
-            #            dest_contents = base64.b64decode(dest_contents)
-            #        else:
-            #            raise Exception("unknown encoding, failed: %s" % dest_result)
+
+            if self._play_context.diff:
+                diff = self._get_diff_data(tmp, dest, path, task_vars)
+
             xfered = self._transfer_data('src', resultant)
 
             # fix file permissions when the copy is done as a different user
@@ -139,8 +135,8 @@ class ActionModule(ActionBase):
             )
 
             res = self._execute_module(module_name='copy', module_args=new_module_args, task_vars=task_vars, tmp=tmp)
-            # FIXME: diff stuff
-            #res.diff = dict(after=resultant)
+            if diff:
+                res['diff'] = diff
             return res
         else:
             new_module_args = self._task.args.copy()