diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index 22f325922..c5ace1287 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -1007,16 +1007,18 @@ class Coder:
         try:
             commit = self.repo.head.commit
         except ValueError:
-            return set()
+            commit = None
 
         files = []
-        for blob in commit.tree.traverse():
-            if blob.type == "blob":  # blob is a file
-                files.append(blob.path)
+        if commit:
+            for blob in commit.tree.traverse():
+                if blob.type == "blob":  # blob is a file
+                    files.append(blob.path)
 
         # Add staged files
         index = self.repo.index
-        staged_files = [item.a_path for item in index.diff("HEAD")]
+        staged_files = [path for path, _ in index.entries.keys()]
+
         files.extend(staged_files)
 
         # convert to appropriate os.sep, since git always normalizes to /