--- a/config/check_spidermonkey_style.py
+++ b/config/check_spidermonkey_style.py
@@ -284,18 +284,18 @@ def check_style():
                 do_file(filename, inclname, file_kind, f, all_inclnames, included_h_inclnames)
 
         edges[inclname] = included_h_inclnames
 
     find_cycles(all_inclnames, edges)
 
     # Compare expected and actual output.
     difflines = difflib.unified_diff(expected_output, actual_output,
-                                     fromfile='check_spider_monkey_style.py expected output',
-                                       tofile='check_spider_monkey_style.py actual output')
+                                     fromfile='check_spidermonkey_style.py expected output',
+                                       tofile='check_spidermonkey_style.py actual output')
     ok = True
     for diffline in difflines:
         ok = False
         print(diffline, end='')
 
     return ok