# Git: How to Merge Branches with Unrelated Histories

> Fix the refusing to merge unrelated histories error in Git by passing the allow-unrelated-histories flag to git merge when combining separate codebases

**URL:** https://sentry.io/answers/merge-branches-with-unrelated-histories-in-git/

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## The Problem

During a Git merge, I encounter the following error message:

```
fatal: refusing to merge unrelated histories
Error redoing merge
```

How can I fix this error and complete the merge?

## The Solution

Git is very flexible and allows us to do things that may not be intuitive for a source control program, such as creating branches in the same repository that have entirely different contents and commit histories. This has some practical uses, such as the `gh-pages` branch used to publish websites on [GitHub Pages](https://pages.github.com/).

However, if we attempt to merge two branches without a common base commit, we will encounter this error, which was [introduced in Git 2.9.0](https://github.com/git/git/blob/master/Documentation/RelNotes/2.9.0.adoc) to prevent accidental merges of this type, as they are quite unusual.

If this error occurs during a merge that is not intended to combine two separate codebases, there may be a problem with our local Git repository. Reclone the remote version of the repository in a different directory and migrate any local changes there before attempting the merge again.

If we are attempting to combine two separate codebases, we must pass the flag [`--allow-unrelated-histories`](https://git-scm.com/docs/git-merge#Documentation/git-merge.txt---allow-unrelated-histories) to `git merge`:

```bash
git merge --allow-unrelated-histories
```

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*Source: [sentry.io/answers/merge-branches-with-unrelated-histories-in-git/](https://sentry.io/answers/merge-branches-with-unrelated-histories-in-git/)*