diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index d7e2bcc18..916132ad4 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -242,6 +242,7 @@ class Coder:
 
         self.verbose = verbose
         self.abs_fnames = set()
+        self.abs_read_only_fnames = set()
 
         if cur_messages:
             self.cur_messages = cur_messages