diff --git a/src/git.ts b/src/git.ts
index 77b4a57..6afb717 100644
--- a/src/git.ts
+++ b/src/git.ts
@@ -51,12 +51,16 @@ export async function createWorktree(branch: string, worktreePath: string, cwd:
   let result
   let switchedFromBranch = false
   if (exists === "local") {
+    const main = await mainBranch(cwd)
+    if (branch === main) {
+      throw new Error(`Cannot create a worktree for the main branch "${main}".`)
+    }
     // If the branch is checked out in the main worktree, switch it to main first
     if (await currentBranch(cwd) === branch) {
       if (await isDirty(cwd)) {
         throw new Error(`Cannot move branch "${branch}" to a worktree: the main worktree has uncommitted changes. Commit or stash them first.`)
       }
-      await checkout(await mainBranch(cwd), cwd)
+      await checkout(main, cwd)
       switchedFromBranch = true
     }
     result = await $`git worktree add ${worktreePath} ${branch}`.cwd(cwd).nothrow().quiet()