diff --git a/doc/api/ssl.rst b/doc/api/ssl.rst
index fbee1fe..4b57ac5 100644
--- a/doc/api/ssl.rst
+++ b/doc/api/ssl.rst
@@ -835,7 +835,9 @@
 
 .. py:method:: Connection.get_next_proto_negotiated():
 
-    Get the protocol that was negotiated by Next Protocol Negotiation.
+    Get the protocol that was negotiated by Next Protocol Negotiation. Returns
+    a bytestring of the protocol name. If no protocol has been negotiated yet,
+    returns an empty string.
 
     .. versionadded:: 0.15