diff --git a/spinnman/transceiver/base_transceiver.py b/spinnman/transceiver/base_transceiver.py
index 89c5bf8d6..30b13a2eb 100644
--- a/spinnman/transceiver/base_transceiver.py
+++ b/spinnman/transceiver/base_transceiver.py
@@ -1146,6 +1146,7 @@ def set_ip_tag(self, ip_tag: IPTag, use_sender: bool = False):
         for connection in connections:
             # Convert the host string
             host_string = ip_tag.ip_address
+            assert host_string is not None
             if host_string in ("localhost", ".", "0.0.0.0"):
                 host_string = connection.local_ip_address
             ip_string = socket.gethostbyname(host_string)