diff --git a/tools/circular_includes.py b/tools/circular_includes.py
index d3d448d55..9ee240013 100755
--- a/tools/circular_includes.py
+++ b/tools/circular_includes.py
@@ -58,7 +58,7 @@ def main(parse_args):
                 file_stack.append(header)
         else:
             # popped back up to an earlier header
-            while file_stack[-1] != header:
+            while (len(file_stack) > 0) and (file_stack[-1] != header):
                 file_stack.pop()
 
     return 0