diff --git a/scripts/zfs-tests.sh b/scripts/zfs-tests.sh
index ae62f8f2a..4a874119e 100755
--- a/scripts/zfs-tests.sh
+++ b/scripts/zfs-tests.sh
@@ -718,6 +718,12 @@ if [ -e /sys/module/zfs/parameters/zfs_dbgmsg_enable ]; then
 	sudo sh -c "echo 0 >/proc/spl/kstat/zfs/dbgmsg"
 fi
 
+#
+# Set TMPDIR. Some tests run mktemp, and we want those files contained to
+# the work dir the same as any other.
+#
+export TMPDIR="$FILEDIR"
+
 msg
 msg "--- Configuration ---"
 msg "Runfiles:        $RUNFILES"
@@ -725,6 +731,7 @@ msg "STF_TOOLS:       $STF_TOOLS"
 msg "STF_SUITE:       $STF_SUITE"
 msg "STF_PATH:        $STF_PATH"
 msg "FILEDIR:         $FILEDIR"
+msg "TMPDIR:          $TMPDIR"
 msg "FILES:           $FILES"
 msg "LOOPBACKS:       $LOOPBACKS"
 msg "DISKS:           $DISKS"
diff --git a/tests/test-runner/bin/test-runner.py.in b/tests/test-runner/bin/test-runner.py.in
index 2538f99ca..abe27d17d 100755
--- a/tests/test-runner/bin/test-runner.py.in
+++ b/tests/test-runner/bin/test-runner.py.in
@@ -238,7 +238,15 @@ User: %s
             if os.path.isfile(cmd+'.sh') and os.access(cmd+'.sh', os.X_OK):
                 cmd += '.sh'
 
-        ret = '%s -E -u %s %s' % (SUDO, user, cmd)
+        # glibc (at least) will not pass TMPDIR through to setuid programs.
+        # if set, arrange for it to be reset before running the target cmd
+        tmpdir = os.getenv('TMPDIR')
+        if tmpdir:
+            tmpdirarg = 'env TMPDIR=%s' % tmpdir
+        else:
+            tmpdirarg = ''
+
+        ret = '%s -E -u %s %s %s' % (SUDO, user, tmpdirarg, cmd)
         return ret.split(' ')
 
     def collect_output(self, proc, debug=False):