diff --git a/spinnman/utilities/locate_connected_machine_ip_address.py b/spinnman/utilities/locate_connected_machine_ip_address.py
index eaa734033..fada9048e 100644
--- a/spinnman/utilities/locate_connected_machine_ip_address.py
+++ b/spinnman/utilities/locate_connected_machine_ip_address.py
@@ -20,7 +20,7 @@
 from spinnman.connections.udp_packet_connections import IPAddressesConnection
 
 
-def locate_connected_machine(handler: Callable[[str, float], None]):
+def locate_connected_machine(handler: Callable[[str, float], None]) -> None:
     """
     Locates any SpiNNaker machines IP addresses from the auto-transmitted
     packets from non-booted SpiNNaker machines.