diff --git a/aider/main.py b/aider/main.py
index b7508d4d8..775e49762 100644
--- a/aider/main.py
+++ b/aider/main.py
@@ -42,9 +42,11 @@ def setup_git(git_root, io):
 
 
 def check_gitignore(git_root, io):
+    if not git_root:
+        return
+
     pat = ".aider*"
 
-    updated_ignore = None
     gitignore_file = Path(git_root) / ".gitignore"
     if gitignore_file.exists():
         content = gitignore_file.read_text(encoding="utf-8")
@@ -56,7 +58,7 @@ def check_gitignore(git_root, io):
     if not io.confirm_ask(f"Add {pat} to .gitignore (recommended)?"):
         return
 
-    if not content.endswith("\n"):
+    if content and not content.endswith("\n"):
         content += "\n"
     content += pat + "\n"
     gitignore_file.write_text(content, encoding="utf-8")
@@ -366,8 +368,6 @@ def main(args=None, input=None, output=None):
 
     if args.git:
         git_root = setup_git(git_root, io)
-
-    if git_root:
         check_gitignore(git_root, io)
 
     def scrub_sensitive_info(text):
diff --git a/tests/test_main.py b/tests/test_main.py
index 847b47c08..ed818cc84 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -12,7 +12,7 @@ from prompt_toolkit.output import DummyOutput
 
 from aider.dump import dump  # noqa: F401
 from aider.io import InputOutput
-from aider.main import main, setup_git
+from aider.main import check_gitignore, main, setup_git
 from tests.utils import make_repo
 
 
@@ -80,6 +80,22 @@ class TestMain(TestCase):
 
         self.assertTrue(git.Repo(self.tempdir))
 
+    def test_check_gitignore(self):
+        make_repo()
+        io = InputOutput(pretty=False, yes=True)
+        cwd = Path.cwd()
+        gitignore = cwd / ".gitignore"
+
+        self.assertFalse(gitignore.exists())
+        check_gitignore(cwd, io)
+        self.assertTrue(gitignore.exists())
+
+        self.assertEqual(".aider*", gitignore.read_text().splitlines()[0])
+
+        gitignore.write_text("one\ntwo\n")
+        check_gitignore(cwd, io)
+        self.assertEqual("one\ntwo\n.aider*\n", gitignore.read_text())
+
     def test_main_args(self):
         with patch("aider.main.Coder.create") as MockCoder:
             # --yes will just ok the git repo without blocking on input