diff --git a/oio-win.c b/oio-win.c
index b88495431..3bae9571a 100644
--- a/oio-win.c
+++ b/oio-win.c
@@ -1311,6 +1311,9 @@ static void oio_poll() {
           }
         }
         break;
+
+      default:
+        assert(0);
     }
 
     /* The number of pending requests is now down by one */