diff --git a/tests/run.sh b/tests/run.sh
index 505fb150..2e0f16a5 100755
--- a/tests/run.sh
+++ b/tests/run.sh
@@ -13,7 +13,7 @@
 set -e
 
 export SHELL=/bin/sh
-export HOME="${TMP:-/tmp}"
+export HOME=/dev/null
 
 # Parse options.
 usage() {