diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 11d93f3ed6..7b391042d9 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -547,6 +547,8 @@ mem_create(const char *name, isc_mem_t **ctxp, unsigned int debugging,
 
 static void
 mem_destroy(isc_mem_t *ctx) {
+	REQUIRE(VALID_CONTEXT(ctx));
+
 	isc_refcount_destroy(&ctx->references);
 
 	LOCK(&contextslock);