diff --git a/tools/pip-micropython b/tools/pip-micropython
index 3d3681198c..0db699f0c0 100755
--- a/tools/pip-micropython
+++ b/tools/pip-micropython
@@ -12,7 +12,7 @@ if [ "$1" != "install" ]; then
 fi
 shift
 
-if [ -n "$TMPDIR" ]; then
+if [ -z "$TMPDIR" ]; then
     TMPDIR=/tmp
 fi
 TMPVENV="$TMPDIR/pip-micropy-venv"