diff --git a/plugins/modules/sts_assume_role.py b/plugins/modules/sts_assume_role.py
index 8283c49d862..7f86c34a475 100644
--- a/plugins/modules/sts_assume_role.py
+++ b/plugins/modules/sts_assume_role.py
@@ -73,7 +73,7 @@
     type: dict
     sample:
       access_key: XXXXXXXXXXXXXXXXXXXX
-      expiration: 2017-11-11T11:11:11+00:00
+      expiration: '2017-11-11T11:11:11+00:00'
       secret_key: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
       session_token: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 sts_user: