diff --git a/src/lib/commands/miss.c b/src/lib/commands/miss.c
index bea774b4..ceadc334 100644
--- a/src/lib/commands/miss.c
+++ b/src/lib/commands/miss.c
@@ -204,6 +204,9 @@ mission(void)
     case EF_PLANE:
 	mobmax = plane_mob_max;
 	break;
+    default:
+	CANT_HAPPEN("bad TYPE");
+	return RET_FAIL;
     }
 
     mobused = ldround((mission_mob_cost * (double)mobmax), 1);