diff --git a/aider/io.py b/aider/io.py
index 3ee5b8317..41299ae2a 100644
--- a/aider/io.py
+++ b/aider/io.py
@@ -39,8 +39,11 @@ class AutoCompleter(Completer):
             self.words.add(rel_fname)
 
             fname = os.path.join(root, rel_fname)
-            with open(fname, "r") as f:
-                content = f.read()
+            try:
+                with open(fname, "r") as f:
+                    content = f.read()
+            except FileNotFoundError:
+                continue
             try:
                 lexer = guess_lexer_for_filename(fname, content)
             except ClassNotFound:
diff --git a/tests/test_io.py b/tests/test_io.py
index 6863384a4..c1350b03a 100644
--- a/tests/test_io.py
+++ b/tests/test_io.py
@@ -2,7 +2,7 @@ import os
 import unittest
 from unittest.mock import patch
 
-from aider.io import InputOutput, AutoCompleter
+from aider.io import AutoCompleter, InputOutput
 
 
 class TestInputOutput(unittest.TestCase):
@@ -13,11 +13,11 @@ class TestInputOutput(unittest.TestCase):
 
     def test_autocompleter_with_non_existent_file(self):
         root = ""
-        rel_fnames = ["non_existent_file"]
+        rel_fnames = ["non_existent_file.txt"]
         addable_rel_fnames = []
         commands = None
         autocompleter = AutoCompleter(root, rel_fnames, addable_rel_fnames, commands)
-        self.assertEqual(autocompleter.words, set())
+        self.assertEqual(autocompleter.words, set(rel_fnames))
 
 
 if __name__ == "__main__":