diff --git a/install_spack_env.sh b/install_spack_env.sh
index 312326254bde83a0a532d0e3690aaf0aa97166b2..a0ed1f67a75ffc4d7f740871259abbf95f5ae258 100644
--- a/install_spack_env.sh
+++ b/install_spack_env.sh
@@ -130,7 +130,7 @@ spack-python -c "exit(not len(spack.environment.active_environment().uninstalled
     else
         echo "Updating of the source cache disabled."
     fi
-    if [ $ret -ne 0 ]; then
+    if [ "$ret" -ne 0 ]; then
         (exit $ret)
     fi
 )