diff --git a/lib/datastruct/kvpair.c b/lib/datastruct/kvpair.c
index 87743a1d..9db56b02 100644
--- a/lib/datastruct/kvpair.c
+++ b/lib/datastruct/kvpair.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <stdlib.h>
 
 #include "kvldskey.h"
@@ -45,6 +46,9 @@ void
 kvpair_sort(struct kvpair * pairs, size_t npairs, size_t mlen)
 {
 
+	/* Sanity check. */
+	assert(pairs != NULL);
+
 	/* See above comments about cookie_mlen and non-threadsafety. */
 	cookie_mlen = mlen;