diff --git a/local/scripts/sync-versions.sh b/local/scripts/sync-versions.sh
index c2178098dc..2633811c4c 100755
--- a/local/scripts/sync-versions.sh
+++ b/local/scripts/sync-versions.sh
@@ -104,6 +104,16 @@ should_exclude() {
         [[ "$path" == *"$ex"* ]] && return 0
     done
 
+    # Skip git-fetched upstream sources. Fetched recipe sources (e.g. brush
+    # from github) live in gitignored, untracked source/ trees; their crate
+    # versions belong to upstream, not to the Cat 1 in-house branch-version
+    # policy. Rewriting them breaks upstream-internal version requirements
+    # (this happened: brush-shell was forced to 0.3.1 while brush required
+    # ^0.4.0, breaking the build). In-house crates are tracked trees.
+    if ! git ls-files --error-unmatch "$path" >/dev/null 2>&1; then
+        return 0
+    fi
+
     return 1
 }