diff --git a/usr.bin/mkimg/image.c b/usr.bin/mkimg/image.c
index e92b1f278791..e8dc8fe2082f 100644
--- a/usr.bin/mkimg/image.c
+++ b/usr.bin/mkimg/image.c
@@ -30,6 +30,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <assert.h>
 #include <errno.h>
+#include <limits.h>
+#include <paths.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
@@ -38,7 +41,7 @@ __FBSDID("$FreeBSD$");
 
 #define	BUFFER_SIZE	(1024*1024)
 
-static char image_tmpfile[] = "/tmp/mkimg-XXXXXX";
+static char image_tmpfile[PATH_MAX];
 static int image_fd = -1;
 static lba_t image_size;
 
@@ -161,9 +164,14 @@ image_write(lba_t blk, void *buf, ssize_t len)
 int
 image_init(void)
 {
+	const char *tmpdir;
 
 	if (atexit(cleanup) == -1)
 		return (errno);
+	if ((tmpdir = getenv("TMPDIR")) == NULL || *tmpdir == '\0')
+		tmpdir = _PATH_TMP;
+	snprintf(image_tmpfile, sizeof(image_tmpfile), "%s/mkimg-XXXXXX",
+	    tmpdir);
 	image_fd = mkstemp(image_tmpfile);
 	if (image_fd == -1)
 		return (errno);
diff --git a/usr.bin/mkimg/mkimg.1 b/usr.bin/mkimg/mkimg.1
index f5144bef871c..cf86308ab680 100644
--- a/usr.bin/mkimg/mkimg.1
+++ b/usr.bin/mkimg/mkimg.1
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 27, 2014
+.Dd May 22, 2014
 .Dt MKIMG 1
 .Os
 .Sh NAME
@@ -159,6 +159,11 @@ For partitioning schemes that feature partition labels, the
 utility supports assigning labels to the partitions specified.
 In the following example the file system partition is labeled as 'backup':
 .Dl % mkimg -s gpt -p freebsd-ufs/backup:=file-system.ufs -o gpt.img
+.Sh ENVIRONMENT
+.Bl -tag -width "TMPDIR" -compact
+.It Ev TMPDIR
+Directory to put temporary files in; default is
+.Pa /tmp .
 .Sh SEE ALSO
 .Xr gpart 8
 .Xr makefs 8