diff --git a/control/gen-fan-zone-defs.py b/control/gen-fan-zone-defs.py
index 7db3d95..e875e32 100755
--- a/control/gen-fan-zone-defs.py
+++ b/control/gen-fan-zone-defs.py
@@ -810,6 +810,7 @@
                 profiles = z['cooling_profiles']
 
             # 'interfaces' is optional (no default)
+            ifaces = []
             if ('interfaces' in z) and \
                     (z['interfaces'] is not None):
                 ifaces = getIfacesInZone(z['interfaces'])