diff --git a/docs/hazmat/primitives/interfaces.rst b/docs/hazmat/primitives/interfaces.rst
index bffd3e2..2ee2017 100644
--- a/docs/hazmat/primitives/interfaces.rst
+++ b/docs/hazmat/primitives/interfaces.rst
@@ -669,7 +669,7 @@
 
     .. method:: update(data)
 
-        :param data bytes: The data you want to authenticate
+        :param data bytes: The data you want to authenticate.
 
     .. method:: finalize()