diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index dc93b547d..8175965ad 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -434,13 +434,7 @@ class Coder:
             bold = False
 
     def find_common_root(self):
-        if len(self.abs_fnames) == 1:
-            self.root = os.path.dirname(list(self.abs_fnames)[0])
-        elif self.abs_fnames:
-            self.root = os.path.commonpath(list(self.abs_fnames))
-        else:
-            self.root = os.getcwd()
-
+        self.root = utils.find_common_root(self.abs_fnames)
         self.root = utils.safe_abs_path(self.root)
 
     def add_rel_fname(self, rel_fname):
diff --git a/aider/utils.py b/aider/utils.py
index d0a8e5130..ca4d6213d 100644
--- a/aider/utils.py
+++ b/aider/utils.py
@@ -272,6 +272,16 @@ class Spinner:
             print("\r" + " " * (len(self.text) + 3))
 
 
+import os
+
+def find_common_root(abs_fnames):
+    if len(abs_fnames) == 1:
+        return os.path.dirname(list(abs_fnames)[0])
+    elif abs_fnames:
+        return os.path.commonpath(list(abs_fnames))
+    else:
+        return os.getcwd()
+
 def check_pip_install_extra(io, module, prompt, pip_install_cmd):
     try:
         __import__(module)