diff --git a/README.md b/README.md
index 4b28e5c1a..a6847e842 100644
--- a/README.md
+++ b/README.md
@@ -225,6 +225,7 @@ options.
 | :-------- | :---------- | :---- | :-------------------------------------------------------------------------- | ------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | lock file | `lock_file` | `str` | dictates which lock file `buildbot-nix` will use when evaluating your flake | `flake.lock` | have multiple lockfiles, one for `nixpkgs-stable`, one for `nixpkgs-unstable` or by default pin an input to a private repo, but have a lockfile with that private repo replaced by a public repo for CI |
 | attribute | `attribute` | `str` | which attribute in the flake to evaluate and build                          | `checks`     | using a different attribute, like `hydraJobs`                                                                                                                                                           |
+| flake_dir | `flake_dir` | `str` | which directory the flake is located                                        | `.`          | using a different flake, like `./tests`                                                                                                                                                                 |
 
 ## Binary caches
 
diff --git a/buildbot_nix/buildbot_nix/__init__.py b/buildbot_nix/buildbot_nix/__init__.py
index 4b7414151..ef2f6a0ac 100644
--- a/buildbot_nix/buildbot_nix/__init__.py
+++ b/buildbot_nix/buildbot_nix/__init__.py
@@ -176,7 +176,7 @@ async def run(self) -> int:
                 "--force-recurse",
                 "--check-cache-status",
                 "--flake",
-                f".#{branch_config.attribute}",
+                f"{branch_config.flake_dir}#{branch_config.attribute}",
                 *(
                     ["--reference-lock-file", branch_config.lock_file]
                     if branch_config.lock_file != "flake.lock"
diff --git a/buildbot_nix/buildbot_nix/repo_config/__init__.py b/buildbot_nix/buildbot_nix/repo_config/__init__.py
index 59591fc1c..e32e4b647 100644
--- a/buildbot_nix/buildbot_nix/repo_config/__init__.py
+++ b/buildbot_nix/buildbot_nix/repo_config/__init__.py
@@ -1,10 +1,13 @@
 import tomllib
+from pathlib import Path
 from tomllib import TOMLDecodeError
 from typing import TYPE_CHECKING, Self
 
 from buildbot.process.buildstep import BuildStep, ShellMixin
 from pydantic import BaseModel, ValidationError
 
+from buildbot_nix.errors import BuildbotNixError
+
 if TYPE_CHECKING:
     from buildbot.process.log import StreamLog
 
@@ -18,6 +21,7 @@ class RepoConfig(BaseModel):
 
 
 class BranchConfig(BaseModel):
+    flake_dir: str = "."
     lock_file: str = "flake.lock"
     attribute: str = "checks"
 
@@ -43,10 +47,16 @@ async def extract_during_step(cls, buildstep: BuildStepShellMixin) -> Self:
             )
             return cls()
         try:
-            return cls.model_validate(tomllib.loads(cmd.stdout))
+            config = cls.model_validate(tomllib.loads(cmd.stdout))
+            flake_dir = Path(config.flake_dir).resolve()
+            root_dir = Path.cwd().resolve()
+            if ":" in config.flake_dir or not flake_dir.is_relative_to(root_dir):
+                msg = f"Invalid flake_dir {config.flake_dir}"
+                raise BuildbotNixError(msg)
         except ValidationError as e:
             stdio.addStderr(f"Failed to read repository local configuration, {e}.\n")
             return cls()
         except TOMLDecodeError as e:
             stdio.addStderr(f"Failed to read repository local configuration, {e}.\n")
             return cls()
+        return config