diff --git a/s6/debian-root/etc/cont-init.d/20-start.sh b/s6/debian-root/etc/cont-init.d/20-start.sh
index 3275925..1f68689 100644
--- a/s6/debian-root/etc/cont-init.d/20-start.sh
+++ b/s6/debian-root/etc/cont-init.d/20-start.sh
@@ -14,7 +14,7 @@ $bashCmd /start.sh
 if [ -n "$PYTEST" ]; then 
     sed -i 's/^gravity_spinup$/#gravity_spinup # DISABLED FOR PYTEST/g' "$(which gravity.sh)" 
 fi
-if [ ! -n "$SKIPGRAVITYONBOOT" ]; then
+if [ -z "$SKIPGRAVITYONBOOT" ]; then
     gravity.sh
 fi