diff --git a/CHANGES b/CHANGES
index 9e843dc630..c7fbf7a647 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+3283.	[bug]		Raw zones with with more than 512 records in a RRset
+			failed to load. [RT #27863]
+
 3282.	[bug]		Restrict the TTL of NS RRset to no more than that
 			of the old NS RRset when replacing it. [RT #27792]
 
diff --git a/bin/tests/system/masterformat/clean.sh b/bin/tests/system/masterformat/clean.sh
index 5c2f13d939..b826048023 100755
--- a/bin/tests/system/masterformat/clean.sh
+++ b/bin/tests/system/masterformat/clean.sh
@@ -14,15 +14,18 @@
 # OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 # PERFORMANCE OF THIS SOFTWARE.
 
-# $Id: clean.sh,v 1.10 2011/12/22 07:32:40 each Exp $
+# $Id: clean.sh,v 1.11 2012/02/13 23:46:23 marka Exp $
 
 rm -f named-compilezone
 rm -f ns1/example.db.raw*
 rm -f ns1/example.db.compat
 rm -f ns1/example.db.serial.raw
-rm -f ns2/example.db
+rm -f ns1/large.db ns1/large.db.raw
 rm -f dig.out.*
+rm -f dig.out
 rm -f */named.memstats
+rm -f ns2/example.db
 rm -f ns2/transfer.db.*
 rm -f ns2/formerly-text.db
 rm -f ns2/db-*
+rm -f ns2/large.bk
diff --git a/bin/tests/system/masterformat/ns1/compile.sh b/bin/tests/system/masterformat/ns1/compile.sh
index e778997b21..886ea5e577 100755
--- a/bin/tests/system/masterformat/ns1/compile.sh
+++ b/bin/tests/system/masterformat/ns1/compile.sh
@@ -12,7 +12,7 @@
 # OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 # PERFORMANCE OF THIS SOFTWARE.
 
-# $Id: compile.sh,v 1.9 2011/12/22 07:32:40 each Exp $
+# $Id: compile.sh,v 1.10 2012/02/13 23:46:24 marka Exp $
 
 ../named-compilezone -D -F raw -o example.db.raw example \
         example.db > /dev/null 2>&1
@@ -22,3 +22,4 @@
         example.db > /dev/null 2>&1
 ../named-compilezone -D -F raw -L 3333 -o example.db.serial.raw example \
         example.db > /dev/null 2>&1
+../named-compilezone -D -F raw -o large.db.raw large large.db > /dev/null 2>&1
diff --git a/bin/tests/system/masterformat/ns1/large.db.in b/bin/tests/system/masterformat/ns1/large.db.in
new file mode 100644
index 0000000000..13cc81d2fb
--- /dev/null
+++ b/bin/tests/system/masterformat/ns1/large.db.in
@@ -0,0 +1,27 @@
+; Copyright (C) 2005, 2007  Internet Systems Consortium, Inc. ("ISC")
+;
+; Permission to use, copy, modify, and/or distribute this software for any
+; purpose with or without fee is hereby granted, provided that the above
+; copyright notice and this permission notice appear in all copies.
+;
+; THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+; REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+; AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+; INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+; LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+; OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+; PERFORMANCE OF THIS SOFTWARE.
+
+; $Id: large.db.in,v 1.2 2012/02/13 23:46:24 marka Exp $
+
+$TTL 1D
+
+@			IN SOA	ns hostmaster (
+				1
+				3600
+				1800
+				1814400
+				3
+				)
+			NS	ns
+ns			A	10.53.0.1
diff --git a/bin/tests/system/masterformat/ns1/named.conf b/bin/tests/system/masterformat/ns1/named.conf
index b16c7000ba..8471f8ce9e 100644
--- a/bin/tests/system/masterformat/ns1/named.conf
+++ b/bin/tests/system/masterformat/ns1/named.conf
@@ -14,7 +14,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: named.conf,v 1.7 2011/12/08 16:07:20 each Exp $ */
+/* $Id: named.conf,v 1.8 2012/02/13 23:46:24 marka Exp $ */
 
 // NS1
 
@@ -59,3 +59,10 @@ zone "transfer3" {
         file "example.db";
         allow-transfer { any; };
 };
+
+zone "large" {
+        type master;
+        file "large.db.raw";
+	masterfile-format raw;
+        allow-transfer { any; };
+};
diff --git a/bin/tests/system/masterformat/ns2/named.conf b/bin/tests/system/masterformat/ns2/named.conf
index 6f2c0d2756..45c21e94b7 100644
--- a/bin/tests/system/masterformat/ns2/named.conf
+++ b/bin/tests/system/masterformat/ns2/named.conf
@@ -14,7 +14,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: named.conf,v 1.6 2011/10/26 23:46:15 tbox Exp $ */
+/* $Id: named.conf,v 1.7 2012/02/13 23:46:24 marka Exp $ */
 
 // NS2
 
@@ -53,3 +53,10 @@ zone "transfer3" {
         masters { 10.53.0.1; };
         file "formerly-text.db";
 };
+
+zone "large" {
+        type slave;
+        masters { 10.53.0.1; };
+        masterfile-format raw;
+        file "large.bk";
+};
diff --git a/bin/tests/system/masterformat/setup.sh b/bin/tests/system/masterformat/setup.sh
index ba014a20b1..fce032bbbe 100755
--- a/bin/tests/system/masterformat/setup.sh
+++ b/bin/tests/system/masterformat/setup.sh
@@ -12,11 +12,17 @@
 # OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 # PERFORMANCE OF THIS SOFTWARE.
 
-# $Id: setup.sh,v 1.9 2011/12/08 16:07:20 each Exp $
+# $Id: setup.sh,v 1.10 2012/02/13 23:46:23 marka Exp $
 
 rm -f named-compilezone
 ln -s $CHECKZONE named-compilezone
 rm -f ns1/example.db.raw
 cp ns1/example.db ns2/
 cp ns2/formerly-text.db.in ns2/formerly-text.db
+cp ns1/large.db.in ns1/large.db
+awk 'END {
+	 for (i = 0; i < 512; i++ ) { print "a TXT", i; }
+	 for (i = 0; i < 1024; i++ ) { print "b TXT", i; }
+	 for (i = 0; i < 2000; i++ ) { print "c TXT", i; }
+}' < /dev/null >> ns1/large.db
 cd ns1 && sh compile.sh
diff --git a/bin/tests/system/masterformat/tests.sh b/bin/tests/system/masterformat/tests.sh
index f3310c10dd..839ca578da 100755
--- a/bin/tests/system/masterformat/tests.sh
+++ b/bin/tests/system/masterformat/tests.sh
@@ -14,7 +14,7 @@
 # OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 # PERFORMANCE OF THIS SOFTWARE.
 
-# $Id: tests.sh,v 1.12 2012/02/01 23:46:51 tbox Exp $
+# $Id: tests.sh,v 1.13 2012/02/13 23:46:23 marka Exp $
 
 SYSTEMTESTTOP=..
 . $SYSTEMTESTTOP/conf.sh
@@ -88,7 +88,7 @@ status=`expr $status + $ret`
 echo "I:waiting for transfers to complete"
 for i in 0 1 2 3 4 5 6 7 8 9
 do
-	test -f ns2/transfer.db.raw -a -f ns2/transfer.db.txt  && break
+	test -f ns2/transfer.db.raw -a -f ns2/transfer.db.txt && break
 	sleep 1
 done
 
@@ -116,5 +116,15 @@ done
 [ $ret -eq 0 ] || echo "I:failed"
 status=`expr $status + $ret`
 
+echo "I:checking that large rdatasets loaded"
+ret=0
+for a in a b c
+do
+	$DIG +tcp txt ${a}.large @10.53.0.2 -p 5300 > dig.out
+	grep "status: NOERROR" dig.out > /dev/null || ret=1
+done
+[ $ret -eq 0 ] || echo "I:failed"
+status=`expr $status + $ret`
+
 echo "I:exit status: $status"
 exit $status
diff --git a/lib/dns/master.c b/lib/dns/master.c
index 7fd96a842d..0bf22f0430 100644
--- a/lib/dns/master.c
+++ b/lib/dns/master.c
@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: master.c,v 1.183 2012/01/31 23:47:32 tbox Exp $ */
+/* $Id: master.c,v 1.184 2012/02/13 23:46:24 marka Exp $ */
 
 /*! \file */
 
@@ -2292,14 +2292,14 @@ load_raw(dns_loadctx_t *lctx) {
 		if (rdcount > rdata_size) {
 			dns_rdata_t *new_rdata = NULL;
 
-			new_rdata = grow_rdata(rdata_size + RDSZ, rdata,
+			new_rdata = grow_rdata(rdcount + RDSZ, rdata,
 					       rdata_size, &head,
 					       &dummy, mctx);
 			if (new_rdata == NULL) {
 				result = ISC_R_NOMEMORY;
 				goto cleanup;
 			}
-			rdata_size += RDSZ;
+			rdata_size = rdcount + RDSZ;
 			rdata = new_rdata;
 		}
 
@@ -2756,6 +2756,7 @@ grow_rdatalist(int new_len, dns_rdatalist_t *old, int old_len,
 	}
 	while ((this = ISC_LIST_HEAD(save)) != NULL) {
 		ISC_LIST_UNLINK(save, this, link);
+		INSIST(rdlcount < new_len);
 		new[rdlcount] = *this;
 		ISC_LIST_APPEND(*current, &new[rdlcount], link);
 		rdlcount++;
@@ -2768,6 +2769,7 @@ grow_rdatalist(int new_len, dns_rdatalist_t *old, int old_len,
 	}
 	while ((this = ISC_LIST_HEAD(save)) != NULL) {
 		ISC_LIST_UNLINK(save, this, link);
+		INSIST(rdlcount < new_len);
 		new[rdlcount] = *this;
 		ISC_LIST_APPEND(*glue, &new[rdlcount], link);
 		rdlcount++;
@@ -2811,6 +2813,7 @@ grow_rdata(int new_len, dns_rdata_t *old, int old_len,
 		}
 		while ((rdata = ISC_LIST_HEAD(save)) != NULL) {
 			ISC_LIST_UNLINK(save, rdata, link);
+			INSIST(rdcount < new_len);
 			new[rdcount] = *rdata;
 			ISC_LIST_APPEND(this->rdata, &new[rdcount], link);
 			rdcount++;
@@ -2830,13 +2833,14 @@ grow_rdata(int new_len, dns_rdata_t *old, int old_len,
 		}
 		while ((rdata = ISC_LIST_HEAD(save)) != NULL) {
 			ISC_LIST_UNLINK(save, rdata, link);
+			INSIST(rdcount < new_len);
 			new[rdcount] = *rdata;
 			ISC_LIST_APPEND(this->rdata, &new[rdcount], link);
 			rdcount++;
 		}
 		this = ISC_LIST_NEXT(this, link);
 	}
-	INSIST(rdcount == old_len);
+	INSIST(rdcount == old_len || rdcount == 0);
 	if (old != NULL)
 		isc_mem_put(mctx, old, old_len * sizeof(*old));
 	return (new);