Fixed a type in a docstring
diff --git a/acme/acme/client.py b/acme/acme/client.py
index 776ddb38a11..c3e28ef47f0 100644
--- a/acme/acme/client.py
+++ b/acme/acme/client.py
@@ -340,7 +340,7 @@ def poll_and_request_issuance(
             `PollError` with non-empty ``waiting`` is raised.
 
         :returns: ``(cert, updated_authzrs)`` `tuple` where ``cert`` is
-            the issued certificate (`.messages.CertificateResource.),
+            the issued certificate (`.messages.CertificateResource`),
             and ``updated_authzrs`` is a `tuple` consisting of updated
             Authorization Resources (`.AuthorizationResource`) as
             present in the responses from server, and in the same order
