diff --git a/lib/ansible/modules/files/synchronize.py b/lib/ansible/modules/files/synchronize.py
index 5e6f9b78553..b7d7c07bbbe 100644
--- a/lib/ansible/modules/files/synchronize.py
+++ b/lib/ansible/modules/files/synchronize.py
@@ -146,6 +146,10 @@ options:
     type: bool
     default: 'no'
     version_added: "2.0"
+  private_key:
+    description:
+      - Specify the private key to use for SSH-based rsync connections (e.g. C(~/.ssh/id_rsa))
+    version_added: "1.6"
 notes:
    - rsync must be installed on both the local and remote host.
    - For the C(synchronize) module, the "local host" is the host `the synchronize task originates on`, and the "destination host" is the host