diff --git a/CHANGES b/CHANGES
index 5414629ae9..d1495ddb60 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+3894.	[bug]		Buffers in isc_print_vsnprintf were not properly
+			initialized leading to potential overflows when
+			printing out quad values. [RT #36505]
+
 3892.	[bug]		Setting '-t aaaa' in .digrc had unintended side
 			effects. [RT #36452]
 
diff --git a/lib/isc/include/isc/print.h b/lib/isc/include/isc/print.h
index cd1e38eaf6..84c98b9770 100644
--- a/lib/isc/include/isc/print.h
+++ b/lib/isc/include/isc/print.h
@@ -38,10 +38,13 @@
  */
 #if !defined(ISC_PLATFORM_NEEDVSNPRINTF) && defined(ISC__PRINT_SOURCE)
 #define ISC_PLATFORM_NEEDVSNPRINTF
+#undef snprintf
+#undef vsnprintf
 #endif
 
 #if !defined(ISC_PLATFORM_NEEDSPRINTF) && defined(ISC__PRINT_SOURCE)
 #define ISC_PLATFORM_NEEDSPRINTF
+#undef sprintf
 #endif
 
 /***
diff --git a/lib/isc/print.c b/lib/isc/print.c
index a5e5ba6699..4d5ae50d2f 100644
--- a/lib/isc/print.c
+++ b/lib/isc/print.c
@@ -260,7 +260,7 @@ isc_print_vsnprintf(char *str, size_t size, const char *format, va_list ap) {
 					if (hi != 0)
 						sprintf(buf, "%lu", hi);
 					else
-						buf[0] = '\n';
+						buf[0] = '\0';
 					sprintf(buf + strlen(buf), "%lu", mid);
 					sprintf(buf + strlen(buf), "%lu", lo);
 				}
@@ -317,7 +317,7 @@ isc_print_vsnprintf(char *str, size_t size, const char *format, va_list ap) {
 					if (hi != 0)
 						sprintf(buf, "%lu", hi);
 					else
-						buf[0] = '\n';
+						buf[0] = '\0';
 					sprintf(buf + strlen(buf), "%lu", mid);
 					sprintf(buf + strlen(buf), "%lu", lo);
 				}
diff --git a/lib/isc/tests/Makefile.in b/lib/isc/tests/Makefile.in
index a278a67d22..87004793be 100644
--- a/lib/isc/tests/Makefile.in
+++ b/lib/isc/tests/Makefile.in
@@ -38,12 +38,12 @@ OBJS =		isctest.@O@
 
 SRCS =		isctest.c taskpool_test.c hash_test.c lex_test.c \
 		sockaddr_test.c safe_test.c symtab_test.c parse_test.c \
-		regex_test.c
+		print_test.c regex_test.c
 
 SUBDIRS =
 TARGETS =	taskpool_test@EXEEXT@ hash_test@EXEEXT@ lex_test@EXEEXT@ \
 		sockaddr_test@EXEEXT@ safe_test@EXEEXT@ symtab_test@EXEEXT@ \
-		parse_test@EXEEXT@ regex_test@EXEEXT@
+		parse_test@EXEEXT@ print_test@EXEEXT@ regex_test@EXEEXT@
 
 @BIND9_MAKE_RULES@
 
@@ -71,6 +71,10 @@ sockaddr_test@EXEEXT@: sockaddr_test.@O@ isctest.@O@ ${ISCDEPLIBS}
 	${LIBTOOL_MODE_LINK} ${PURIFY} ${CC} ${CFLAGS} ${LDFLAGS} -o $@ \
 			sockaddr_test.@O@ isctest.@O@ ${ISCLIBS} ${LIBS}
 
+print_test@EXEEXT@: print_test.@O@ ${ISCDEPLIBS} ${top_srcdir}/lib/isc/print.c
+	${LIBTOOL_MODE_LINK} ${PURIFY} ${CC} ${CFLAGS} ${LDFLAGS} -o $@ \
+			print_test.@O@ ${ISCLIBS} ${LIBS}
+
 regex_test@EXEEXT@: regex_test.@O@ ${ISCDEPLIBS}
 	${LIBTOOL_MODE_LINK} ${PURIFY} ${CC} ${CFLAGS} ${LDFLAGS} -o $@ \
 			regex_test.@O@ ${ISCLIBS} ${LIBS}
diff --git a/lib/isc/tests/print_test.c b/lib/isc/tests/print_test.c
new file mode 100644
index 0000000000..3b5ac48dbc
--- /dev/null
+++ b/lib/isc/tests/print_test.c
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2014  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.
+ */
+
+#include <config.h>
+
+#include <atf-c.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/*
+ * Workout if we need to force the inclusion of print.c so we can test
+ * it on all platforms even if we don't include it in libisc.
+ */
+#include <isc/platform.h>
+#if !defined(ISC_PLATFORM_NEEDVSNPRINTF) && !defined(ISC_PLATFORM_NEEDSPRINTF)
+#define ISC__PRINT_SOURCE
+#include "../print.c"
+#else
+#if !defined(ISC_PLATFORM_NEEDVSNPRINTF) || !defined(ISC_PLATFORM_NEEDSPRINTF)
+#define ISC__PRINT_SOURCE
+#endif
+#include <isc/print.h>
+#include <isc/types.h>
+#include <isc/util.h>
+#endif
+
+ATF_TC(snprintf);
+ATF_TC_HEAD(snprintf, tc) {
+	atf_tc_set_md_var(tc, "descr", "snprintf implementation");
+}
+ATF_TC_BODY(snprintf, tc) {
+	char buf[10000];
+	isc_uint64_t ll = 8589934592ULL;
+	int n;
+	
+	UNUSED(tc);
+
+	/*
+	 * 4294967296 <= 8589934592 < 1000000000^2 to verify fix for
+	 * RT#36505.
+	 */
+
+	memset(buf, 0xff, sizeof(buf));
+	n = isc_print_snprintf(buf, sizeof(buf), "%qu", ll);
+	ATF_CHECK_EQ(n, 10);
+	ATF_CHECK_STREQ(buf, "8589934592");
+
+	memset(buf, 0xff, sizeof(buf));
+	n = isc_print_snprintf(buf, sizeof(buf), "%llu", ll);
+	ATF_CHECK_EQ(n, 10);
+	ATF_CHECK_STREQ(buf, "8589934592");
+}
+
+/*
+ * Main
+ */
+ATF_TP_ADD_TCS(tp) {
+	ATF_TP_ADD_TC(tp, snprintf);
+	return (atf_no_error());
+}