diff --git a/website/source/docs/providers/openstack/index.html.markdown b/website/source/docs/providers/openstack/index.html.markdown
index 1b8a4237e..2800bfaf5 100644
--- a/website/source/docs/providers/openstack/index.html.markdown
+++ b/website/source/docs/providers/openstack/index.html.markdown
@@ -73,6 +73,9 @@ The following arguments are supported:
 * `insecure` - (Optional) Explicitly allow the provider to perform
     "insecure" SSL requests. If omitted, default value is `false`
 
+* `cacert_file` - (Optional) Specify a custom CA certificate when communicating
+    over SSL. If omitted, the `OS_CACERT` environment variable is used.
+
 * `endpoint_type` - (Optional) Specify which type of endpoint to use from the
     service catalog. It can be set using the OS_ENDPOINT_TYPE environment
     variable. If not set, public endpoints is used.