diff --git a/src/msg/async/AsyncMessenger.cc b/src/msg/async/AsyncMessenger.cc
index 90bb30dac6487..2a2c290f00b71 100644
--- a/src/msg/async/AsyncMessenger.cc
+++ b/src/msg/async/AsyncMessenger.cc
@@ -820,7 +820,7 @@ Connection *AsyncMessenger::create_anon_connection() {
   return new AsyncConnection(cct, this, &dispatch_queue, w);
 }
 
-int AsyncMessenger::get_proto_version(int peer_type, bool connect)
+int AsyncMessenger::get_proto_version(int peer_type, bool connect) const
 {
   int my_type = my_inst.name.type();
 
diff --git a/src/msg/async/AsyncMessenger.h b/src/msg/async/AsyncMessenger.h
index d4270b8c82896..5073ea9b1abb7 100644
--- a/src/msg/async/AsyncMessenger.h
+++ b/src/msg/async/AsyncMessenger.h
@@ -463,7 +463,7 @@ class AsyncMessenger : public SimplePolicyMessenger {
    * a peer protocol (if it matches our own), the protocol version for the
    * peer (if we're connecting), or our protocol version (if we're accepting).
    */
-  int get_proto_version(int peer_type, bool connect);
+  int get_proto_version(int peer_type, bool connect) const;
 
   /**
    * Fill in the address and peer type for the local connection, which