diff --git a/vswitchd/bridge.c b/vswitchd/bridge.c
index 52adc18e3b7..8594a1428d2 100644
--- a/vswitchd/bridge.c
+++ b/vswitchd/bridge.c
@@ -1997,6 +1997,9 @@ find_local_hw_addr(const struct bridge *br, struct eth_addr *ea,
                 }
             }
 
+            /* A port always has at least one interface. */
+            ovs_assert(iface != NULL);
+
             /* The local port doesn't count (since we're trying to choose its
              * MAC address anyway). */
             if (iface->ofp_port == OFPP_LOCAL) {