diff --git a/apps/ui/src/components/views/board-view.tsx b/apps/ui/src/components/views/board-view.tsx
index 2624514a3..48d068a1e 100644
--- a/apps/ui/src/components/views/board-view.tsx
+++ b/apps/ui/src/components/views/board-view.tsx
@@ -1274,8 +1274,10 @@ export function BoardView() {
         maxConcurrency={maxConcurrency}
         runningAgentsCount={runningAutoTasks.length}
         onConcurrencyChange={(newMaxConcurrency) => {
-          if (currentProject && selectedWorktree) {
-            const branchName = selectedWorktree.isMain ? null : selectedWorktree.branch;
+          if (currentProject) {
+            // If selectedWorktree is undefined or it's the main worktree, branchName will be null.
+            // Otherwise, use the branch name.
+            const branchName = selectedWorktree?.isMain === false ? selectedWorktree.branch : null;
             setMaxConcurrencyForWorktree(currentProject.id, branchName, newMaxConcurrency);
             // Also update backend if auto mode is running
             if (autoMode.isRunning) {