diff --git a/sys/kern/kern_malloc.c b/sys/kern/kern_malloc.c
index 4b707aa171a7..4864277dd7d7 100644
--- a/sys/kern/kern_malloc.c
+++ b/sys/kern/kern_malloc.c
@@ -437,7 +437,7 @@ if (mtp == M_SUBPROC) {
 	    ("realloc: address %p out of range", (void *)addr));
 
 	/* Get the size of the original block */
-	if (slab->us_keg)
+	if (!(slab->us_flags & UMA_SLAB_MALLOC))
 		alloc = slab->us_keg->uk_size;
 	else
 		alloc = slab->us_size;