diff --git a/mkosi.images/system/mkosi.sync b/mkosi.images/system/mkosi.sync
index fef0e3b138..d00a776257 100755
--- a/mkosi.images/system/mkosi.sync
+++ b/mkosi.images/system/mkosi.sync
@@ -9,8 +9,15 @@ fi
 
 PKG_SUBDIR="$(realpath --canonicalize-missing "pkg/$DISTRIBUTION" --relative-to "$PWD")"
 
-if [[ -d "$PKG_SUBDIR/.git" ]] && [[ "$(git -C "$PKG_SUBDIR" rev-parse HEAD)" == "$GIT_COMMIT" ]]; then
-    exit 0
+if [[ -d "$PKG_SUBDIR/.git" ]]; then
+    if [[ "$(git -C "$PKG_SUBDIR" rev-parse HEAD)" == "$GIT_COMMIT" ]]; then
+        exit 0
+    fi
+
+    # If work is being done on the packaging rules in a separate branch, don't touch the checkout.
+    if ! git merge-base --is-ancestor HEAD "origin/$GIT_BRANCH"; then
+        exit 0
+    fi
 fi
 
 if [[ ! -e "$PKG_SUBDIR" ]] || [[ -z "$(ls --almost-all "$PKG_SUBDIR")" ]]; then