diff --git a/tests/api_ping.rs b/tests/api_ping.rs
index b1282c56..8abaf267 100644
--- a/tests/api_ping.rs
+++ b/tests/api_ping.rs
@@ -225,7 +225,9 @@ fn ping_over_socket_returns_version() {
     assert_eq!(value["id"], "req_1");
     assert_eq!(value["result"]["type"], "pong");
     assert_eq!(value["result"]["version"], env!("CARGO_PKG_VERSION"));
-    assert_eq!(value["result"]["protocol"], 4);
+    // Intentionally hardcoded so wire protocol bumps require updating this test.
+    // Changing this value means old clients/servers are no longer compatible.
+    assert_eq!(value["result"]["protocol"], 5);
 
     cleanup_spawned_herdr(child, base);
 }