diff --git a/lib/dns/rdataslab.c b/lib/dns/rdataslab.c
index f7b51df147..941e60a318 100644
--- a/lib/dns/rdataslab.c
+++ b/lib/dns/rdataslab.c
@@ -361,7 +361,9 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 					    ? DNS_RDATASLAB_OFFLINE
 					    : 0;
 		}
-		memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+		if (x[i].rdata.length != 0) {
+			memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+		}
 		rawbuf += x[i].rdata.length;
 	}