diff --git a/tools/distrib/check_copyright.py b/tools/distrib/check_copyright.py
index 7d1045f1e5cf2fd74de1678176b6321bf1b619df..571686b0871349a60ebaab1dfb29fa9acaba5882 100755
--- a/tools/distrib/check_copyright.py
+++ b/tools/distrib/check_copyright.py
@@ -52,6 +52,7 @@ LICENSE_FMT = {
   '.cc': ' * %s',
   '.h': ' * %s',
   '.py': '# %s',
+  '.rb': '# %s',
 }
 
 # pregenerate the actual text that we should have