diff --git a/bootstrap.d/11-apt.sh b/bootstrap.d/11-apt.sh
index 5563ae1..4a4469c 100644
--- a/bootstrap.d/11-apt.sh
+++ b/bootstrap.d/11-apt.sh
@@ -16,7 +16,7 @@ install_readonly files/apt/sources.list "${ETC_DIR}/apt/sources.list"
 
 # Use specified APT server and release
 sed -i "s/\/ftp.debian.org\//\/${APT_SERVER}\//" "${ETC_DIR}/apt/sources.list"
-if [ "$APT_INCLUDES_LATE" = "bullseye" ] || [ "$APT_INCLUDES_LATE" = "testing" ] ; then
+if [ "$RELEASE" = "bullseye" ] || [ "$RELEASE" = "testing" ] ; then
 sed -i "s,stretch\\/updates,testing-security," "${ETC_DIR}/apt/sources.list"
 else
 sed -i "s/ stretch/ ${RELEASE}/" "${ETC_DIR}/apt/sources.list"