diff --git a/aider/coder.py b/aider/coder.py
index 4cc287e85..9e0e08493 100755
--- a/aider/coder.py
+++ b/aider/coder.py
@@ -59,10 +59,12 @@ class Coder:
         self.show_diffs = show_diffs
 
     def find_common_root(self):
-        if not self.abs_fnames:
+        if self.abs_fnames:
+            common_prefix = os.path.commonpath(list(self.abs_fnames))
+            self.root = os.path.dirname(common_prefix)
+        else:
             self.root = os.getcwd()
-        common_prefix = os.path.commonpath(list(self.abs_fnames))
-        self.root = os.path.dirname(common_prefix)
+
         self.console.print(f"[bright_black]Common root directory: {self.root}")
 
     def set_repo(self, cmd_line_fnames):