diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index 9c49deb3dd2138c0b3b27a1b073a99e58d90d3bd..f2554ec0af1161b4c73ca4bd3f7321199c4605d7 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -175,7 +175,9 @@ _cleanup_test_img()
     case "$IMGPROTO" in
 
         nbd)
-            kill $QEMU_NBD_PID
+            if [ -n "$QEMU_NBD_PID" ]; then
+                kill $QEMU_NBD_PID
+            fi
             rm -f "$TEST_IMG_FILE"
             ;;
         file)