diff --git a/src/util/virportallocator.c b/src/util/virportallocator.c
index db95a601c7d4e455dab0122257157698c92c09d6..d48963c1ff9744f0bbc73213c837d9c7627d9939 100644
--- a/src/util/virportallocator.c
+++ b/src/util/virportallocator.c
@@ -294,6 +294,9 @@ virPortAllocatorSetUsed(unsigned short port)
     if (!pa)
         return -1;
 
+    if (!port)
+        return 0;
+
     virObjectLock(pa);
 
     if (virBitmapIsBitSet(pa->bitmap, port) ||