diff --git a/crates/worktree/src/worktree.rs b/crates/worktree/src/worktree.rs
index 8d66c375a24168e82af11e3eac022366fe288f1c..55d40e1416307622f71c244dc12e79884a76bbac 100644
--- a/crates/worktree/src/worktree.rs
+++ b/crates/worktree/src/worktree.rs
@@ -5318,16 +5318,13 @@ impl BackgroundScanner {
             match existing_repository_entry {
                 None => {
                     let Ok(relative) = dot_git_dir.strip_prefix(state.snapshot.abs_path()) else {
-                        // This can happen legitimately when `.git` is a
-                        // gitfile (e.g. in a linked worktree or submodule)
-                        // pointing to a directory outside the worktree root.
-                        // Skip it — the repository was already registered
-                        // during the initial scan via `discover_git_paths`.
-                        debug_assert!(
-                            self.fs.is_file(&dot_git_dir).await,
-                            "update_git_repositories: .git path outside worktree root \
-                             is not a gitfile: {dot_git_dir:?}",
-                        );
+                        // A `.git` path outside the worktree root is not
+                        // ours to register. This happens legitimately when
+                        // `.git` is a gitfile pointing outside the worktree
+                        // (linked worktrees and submodules), and also when
+                        // a rescan of a linked worktree's commondir arrives
+                        // after the worktree's repository has already been
+                        // unregistered.
                         continue;
                     };
                     affected_repo_roots.push(dot_git_dir.parent().unwrap().into());
diff --git a/crates/worktree/tests/integration/main.rs b/crates/worktree/tests/integration/main.rs
index 76034c7f5fa01cd50f254fec241ed830c5f90b08..8b6a03fd1f02e725dc119283007798745ffdcaed 100644
--- a/crates/worktree/tests/integration/main.rs
+++ b/crates/worktree/tests/integration/main.rs
@@ -2913,6 +2913,78 @@ async fn test_linked_worktree_git_file_event_does_not_panic(
     });
 }
 
+#[gpui::test]
+async fn test_linked_worktree_event_in_unregistered_common_git_dir_does_not_panic(
+    executor: BackgroundExecutor,
+    cx: &mut TestAppContext,
+) {
+    // Regression test: a rescan event on a linked worktree's commondir
+    // must not panic when the worktree's repository has already been
+    // unregistered from `git_repositories`.
+    init_test(cx);
+
+    use git::repository::Worktree as GitWorktree;
+
+    let fs = FakeFs::new(executor);
+
+    fs.insert_tree(
+        path!("/main_repo"),
+        json!({
+            ".git": {},
+            "file.txt": "content",
+        }),
+    )
+    .await;
+    fs.add_linked_worktree_for_repo(
+        Path::new(path!("/main_repo/.git")),
+        false,
+        GitWorktree {
+            path: PathBuf::from(path!("/linked_worktree")),
+            ref_name: Some("refs/heads/feature".into()),
+            sha: "abc123".into(),
+            is_main: false,
+            is_bare: false,
+        },
+    )
+    .await;
+    fs.write(
+        path!("/linked_worktree/file.txt").as_ref(),
+        "content".as_bytes(),
+    )
+    .await
+    .unwrap();
+
+    let tree = Worktree::local(
+        path!("/linked_worktree").as_ref(),
+        true,
+        fs.clone(),
+        Arc::default(),
+        true,
+        WorktreeId::from_proto(0),
+        &mut cx.to_async(),
+    )
+    .await
+    .unwrap();
+    tree.update(cx, |tree, _| tree.as_local().unwrap().scan_complete())
+        .await;
+    cx.run_until_parked();
+
+    // Unregister the linked worktree's repository by removing its gitfile.
+    fs.remove_file(
+        Path::new(path!("/linked_worktree/.git")),
+        Default::default(),
+    )
+    .await
+    .unwrap();
+    tree.flush_fs_events(cx).await;
+
+    // Deliver the kind of Rescan event `FsWatcher` emits when the kernel
+    // signals `need_rescan` for the commondir.
+    fs.emit_fs_event(path!("/main_repo/.git"), Some(fs::PathEventKind::Rescan));
+    cx.run_until_parked();
+    tree.flush_fs_events(cx).await;
+}
+
 fn init_test(cx: &mut gpui::TestAppContext) {
     zlog::init_test();