diff --git a/CHANGES b/CHANGES
index 64cced24c8..ba22d0708d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+4984.	[bug]		Improve handling of very large incremental
+			zone transfers to prevent journal corruption. [GL #339]
+
 4979.	[bug]		Non-libcap builds were not checking whether all
 			requested capabilities are present in the permitted
 			capability set. [GL #321]
diff --git a/doc/arm/notes.xml b/doc/arm/notes.xml
index b301b5b287..7f2a98b69a 100644
--- a/doc/arm/notes.xml
+++ b/doc/arm/notes.xml
@@ -90,6 +90,14 @@
 
   <section xml:id="relnotes_bugs"><info><title>Bug Fixes</title></info>
     <itemizedlist>
+      <listitem>
+	<para>
+	  <command>named</command> now rejects excessively large
+	  incremental (IXFR) zone transfers in order to prevent
+	  possible corruption of journal files which could cause
+	  <command>named</command> to abort when loading zones. [GL #339]
+	</para>
+      </listitem>
       <listitem>
 	<para>
 	  <command>rndc reload</command> could cause <command>named</command>
diff --git a/lib/dns/journal.c b/lib/dns/journal.c
index da70007f9a..9aab656d41 100644
--- a/lib/dns/journal.c
+++ b/lib/dns/journal.c
@@ -14,8 +14,6 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: journal.c,v 1.120 2011/12/22 07:32:41 each Exp $ */
-
 #include <config.h>
 
 #include <stdlib.h>
@@ -1013,7 +1011,7 @@ dns_journal_writediff(dns_journal_t *j, dns_diff_t *diff) {
 	dns_difftuple_t *t;
 	isc_buffer_t buffer;
 	void *mem = NULL;
-	unsigned int size;
+	isc_uint64_t size;
 	isc_result_t result;
 	isc_region_t used;
 
@@ -1043,6 +1041,14 @@ dns_journal_writediff(dns_journal_t *j, dns_diff_t *diff) {
 		size += t->rdata.length;
 	}
 
+	if (size >= ISC_INT32_MAX) {
+		isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
+			      "dns_journal_writediff: %s: journal entry "
+			      "too big to be stored: %llu bytes", j->filename,
+			      size);
+		return (ISC_R_NOSPACE);
+	}
+
 	mem = isc_mem_get(j->mctx, size);
 	if (mem == NULL)
 		return (ISC_R_NOMEMORY);
@@ -1096,6 +1102,7 @@ isc_result_t
 dns_journal_commit(dns_journal_t *j) {
 	isc_result_t result;
 	journal_rawheader_t rawheader;
+	isc_uint64_t total;
 
 	REQUIRE(DNS_JOURNAL_VALID(j));
 	REQUIRE(j->state == JOURNAL_STATE_TRANSACTION ||
@@ -1145,6 +1152,18 @@ dns_journal_commit(dns_journal_t *j) {
 		}
 	}
 
+	/*
+	 * We currently don't support huge journal entries.
+	 */
+	total = j->x.pos[1].offset - j->x.pos[0].offset;
+	if (total >= ISC_INT32_MAX) {
+		isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
+			     "transaction too big to be stored in journal: "
+			     "%llub (max is %llub)", total,
+			     (isc_uint64_t)ISC_INT32_MAX);
+		return (ISC_R_UNEXPECTED);
+	}
+
 	/*
 	 * Some old journal entries may become non-addressable
 	 * when we increment the current serial number.  Purge them
@@ -1670,7 +1689,12 @@ read_one_rr(dns_journal_t *j) {
 	journal_xhdr_t xhdr;
 	journal_rrhdr_t rrhdr;
 
-	INSIST(j->offset <= j->it.epos.offset);
+	if (j->offset > j->it.epos.offset) {
+		isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
+			      "%s: journal corrupt: possible integer overflow",
+			      j->filename);
+		return (ISC_R_UNEXPECTED);
+	}
 	if (j->offset == j->it.epos.offset)
 		return (ISC_R_NOMORE);
 	if (j->it.xpos == j->it.xsize) {
diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index 7971f7ffa0..85b6008498 100644
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -14281,8 +14281,14 @@ zone_replacedb(dns_zone_t *zone, dns_db_t *db, isc_boolean_t dump) {
 
 		result = dns_db_diff(zone->mctx, db, ver, zone->db, NULL,
 				     zone->journal);
-		if (result != ISC_R_SUCCESS)
-			goto fail;
+		if (result != ISC_R_SUCCESS) {
+			char strbuf[ISC_STRERRORSIZE];
+			isc__strerror(errno, strbuf, sizeof(strbuf));
+			dns_zone_log(zone, ISC_LOG_ERROR,
+				     "ixfr-from-differences: failed: "
+				     "%s", strbuf);
+			goto fallback;
+		}
 		if (dump)
 			zone_needdump(zone, DNS_DUMP_DELAY);
 		else if (zone->journalsize != -1) {
@@ -14306,6 +14312,7 @@ zone_replacedb(dns_zone_t *zone, dns_db_t *db, isc_boolean_t dump) {
 		if (zone->type == dns_zone_master && inline_raw(zone))
 			zone_send_secureserial(zone, serial);
 	} else {
+ fallback:
 		if (dump && zone->masterfile != NULL) {
 			/*
 			 * If DNS_ZONEFLG_FORCEXFER was set we don't want