diff --git a/sys/kern/kern_malloc.c b/sys/kern/kern_malloc.c
--- a/sys/kern/kern_malloc.c
+++ b/sys/kern/kern_malloc.c
@@ -797,7 +797,7 @@
 	void *res;
 	size_t asize;
 
-	KASSERT(align != 0 && powerof2(align),
+	KASSERT(powerof2(align),
 	    ("malloc_domainset_aligned: wrong align %#zx size %#zx",
 	    align, size));
 	KASSERT(align <= PAGE_SIZE,
@@ -812,6 +812,8 @@
 	 * align, since malloc zones provide alignment equal to their
 	 * size.
 	 */
+	if (size == 0)
+		size = 1;
 	asize = size <= align ? align : 1UL << flsl(size - 1);
 
 	res = malloc_domainset(asize, mtp, ds, flags);