diff --git a/lib/ansible/plugins/action/synchronize.py b/lib/ansible/plugins/action/synchronize.py
index 3d2b7c7b081..b92490039b5 100644
--- a/lib/ansible/plugins/action/synchronize.py
+++ b/lib/ansible/plugins/action/synchronize.py
@@ -354,10 +354,13 @@ class ActionModule(ActionBase):
         # If launching synchronize against docker container
         # use rsync_opts to support container to override rsh options
         if self._remote_transport in [ 'docker' ]:
+            if not isinstance(self._task.args.get('rsync_opts'), list):
+                self._task.args['rsync_opts'] = []
+            self._task.args['rsync_opts'].append('--blocking-io')
             if user is not None:
-                self._task.args['rsync_opts'] = "--rsh='%s exec -u %s -i'" % (self._docker_cmd, user)
+                self._task.args['rsync_opts'].append("--rsh='%s exec -u %s -i'" % (self._docker_cmd, user))
             else:
-                self._task.args['rsync_opts'] = "--rsh='%s exec -i'" % (self._docker_cmd)
+                self._task.args['rsync_opts'].append("--rsh='%s exec -i'" % self._docker_cmd)
 
         # run the module and store the result
         result.update(self._execute_module('synchronize', task_vars=task_vars))