diff --git a/tools/pve/post-pve-install.sh b/tools/pve/post-pve-install.sh
index ba32060c..42df5d77 100644
--- a/tools/pve/post-pve-install.sh
+++ b/tools/pve/post-pve-install.sh
@@ -197,7 +197,7 @@ start_routines_9() {
 
       # Check sources.list
       if [[ -f "$listfile" ]] && grep -qE '^\s*deb ' "$listfile"; then
-        ((++ LEGACY_COUNT ))
+        (( ++LEGACY_COUNT ))
       fi
 
       # Check .list files