diff --git a/aider/utils.py b/aider/utils.py
index 139ce4151..54ecc5b05 100644
--- a/aider/utils.py
+++ b/aider/utils.py
@@ -44,7 +44,10 @@ def replace_most_similar_chunk(whole, part, replace):
         + replace_lines
         + whole_lines[most_similar_chunk_end:]
     )
-    modified_whole = "\n".join(modified_whole) + "\n"
+    modified_whole = "\n".join(modified_whole)
+
+    if whole.endswith("\n"):
+        modified_whole += "\n"
 
     return modified_whole
 
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 71b740dba..5c76610c7 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -4,10 +4,10 @@ from aider.utils import replace_most_similar_chunk, strip_quoted_wrapping
 
 class TestUtils(unittest.TestCase):
     def test_replace_most_similar_chunk(self):
-        whole = "This is a sample text.\nAnother line of text.\nYet another line."
+        whole = "This is a sample text.\nAnother line of text.\nYet another line.\n"
         part = "This is a sample text"
         replace = "This is a replaced text."
-        expected_output = "This is a replaced text.\nAnother line of text.\nYet another line."
+        expected_output = "This is a replaced text..\nAnother line of text.\nYet another line.\n"
 
         result = replace_most_similar_chunk(whole, part, replace)
         self.assertEqual(result, expected_output)