diff --git a/lib/dns/acache.c b/lib/dns/acache.c
index fbd8c91025..4142604398 100644
--- a/lib/dns/acache.c
+++ b/lib/dns/acache.c
@@ -14,7 +14,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: acache.c,v 1.12 2006/04/26 12:03:08 shane Exp $ */
+/* $Id: acache.c,v 1.13 2006/04/26 12:12:45 shane Exp $ */
 
 #include <config.h>
 
@@ -1247,6 +1247,21 @@ dns_acache_createentry(dns_acache_t *acache, dns_db_t *origdb,
 	REQUIRE(entryp != NULL && *entryp == NULL);
 	REQUIRE(origdb != NULL);
 
+	/* 
+	 * Should we exceed our memory limit for some reason (for 
+	 * example, if the cleaner does not run aggressively enough), 
+	 * then we will not create additional entries.
+	 *
+	 * XXX: It might be better to lock the acache->cleaner->lock,
+	 * but locking may be an expensive bottleneck. If we misread 
+	 * the value, we will occasionally refuse to create a few 
+	 * cache entries, or create a few that we should not. I do not
+	 * expect this to happen often, and it will not have very bad
+	 * effects when it does. So no lock for now.
+	 */
+	if (acache->cleaner.overmem)
+		return (ISC_R_NORESOURCES);
+
 	newentry = isc_mem_get(acache->mctx, sizeof(*newentry));
 	if (newentry == NULL)
 		return (ISC_R_NOMEMORY);