diff --git a/misc/build.func b/misc/build.func
index 0ef0d4a5b7..d895d3c8d8 100644
--- a/misc/build.func
+++ b/misc/build.func
@@ -1338,7 +1338,8 @@ EOF'
     pct exec "$CTID" -- ash -c "apk add bash newt curl openssh nano mc ncurses jq >/dev/null"
   else
     sleep 3
-    pct exec "$CTID" -- bash -c "sed -i '/$LANG/ s/^# //' /etc/locale.gen"
+    LANG=${LANG:-en_US.UTF-8}
+    pct exec "$CTID" -- bash -c "sed -i \"/$LANG/ s/^# //\" /etc/locale.gen"
     pct exec "$CTID" -- bash -c "locale_line=\$(grep -v '^#' /etc/locale.gen | grep -E '^[a-zA-Z]' | awk '{print \$1}' | head -n 1) && \
     echo LANG=\$locale_line >/etc/default/locale && \
     locale-gen >/dev/null && \