diff --git a/src/git_rebase_branches.py b/src/git_rebase_branches.py
index 6a4792e..e1948c6 100755
--- a/src/git_rebase_branches.py
+++ b/src/git_rebase_branches.py
@@ -53,7 +53,14 @@ def cli(parser: Optional[argparse.ArgumentParser] = None) -> argparse.ArgumentPa
 def branches_that_do_not_contain(ref: str, /) -> list[str]:
     """Get a list of branches that do not contain a given ref."""
     result = run(
-        ["git", "branch", "--no-contains", ref, "--format=%(refname:short)"],
+        [
+            "git",
+            "for-each-ref",
+            "--no-contains",
+            ref,
+            "--format=%(refname:short)",
+            "refs/heads/",
+        ],
         capture_output=True,
         check=True,
         encoding="utf-8",
diff --git a/tests/test_git_rebase_branches.py b/tests/test_git_rebase_branches.py
index 734801d..ba236c6 100644
--- a/tests/test_git_rebase_branches.py
+++ b/tests/test_git_rebase_branches.py
@@ -34,7 +34,8 @@ def branch_commit():
     }
 
 
-def test_git_rebase_branches(tmp_path, monkeypatch):
+@pytest.mark.parametrize("detached", [False, True])
+def test_git_rebase_branches(tmp_path, monkeypatch, detached):
     """Test a basic example."""
     base_ref = "main"
     branch_no_contains = "init"
@@ -42,7 +43,7 @@ def test_git_rebase_branches(tmp_path, monkeypatch):
 
     monkeypatch.chdir(tmp_path)
     commit_opts = ["--allow-empty"]
-    for git_command in [
+    commands = [
         ["init", "-b", base_ref],
         ["config", "commit.gpgsign", "false"],
         ["config", "user.name", "Coder Joe"],
@@ -51,14 +52,17 @@ def test_git_rebase_branches(tmp_path, monkeypatch):
         ["branch", branch_no_contains],
         ["commit"] + commit_opts + ["-m", "New Commit on main"],
         ["branch", branch_contains],
-    ]:
+    ]
+    if detached:
+        commands.append(["switch", "-d", branch_no_contains])
+    for git_command in commands:
         subprocess.run(["git"] + git_command, check=True)
 
-    head = git_rebase_branches.ref_commit("HEAD")
+    commit = git_rebase_branches.ref_commit(base_ref)
     target_state = {
-        base_ref: head,
-        branch_no_contains: head,
-        branch_contains: head,
+        base_ref: commit,
+        branch_no_contains: commit,
+        branch_contains: commit,
     }
     assert branch_commit() != target_state