diff --git a/mypy.bash b/mypy.bash
index c8d73948d..918ce5e9a 100755
--- a/mypy.bash
+++ b/mypy.bash
@@ -22,4 +22,4 @@
 utils="../SpiNNUtils/spinn_utilities"
 machine="../SpiNNMachine/spinn_machine"
 
-mypy $utils $machine spinnman
+mypy --python-version 3.8 $utils $machine spinnman
diff --git a/spinnman/connections/udp_packet_connections/udp_connection.py b/spinnman/connections/udp_packet_connections/udp_connection.py
index b4ae01e98..bf8f87101 100644
--- a/spinnman/connections/udp_packet_connections/udp_connection.py
+++ b/spinnman/connections/udp_packet_connections/udp_connection.py
@@ -140,6 +140,7 @@ def is_connected(self) -> bool:
         # check if machine is active and on the network
         for _ in range(_PING_COUNT):
             # Assume connected if ping works
+            assert self._remote_ip_address is not None
             if Ping.ping(self._remote_ip_address) == 0:
                 return True