diff --git a/.hgignore b/.hgignore
index 2375ef17..eab4df7b 100644
--- a/.hgignore
+++ b/.hgignore
@@ -13,7 +13,6 @@ autom4te.cache
 config.log
 config.status
 include/setup.h
-include/serno.h
 libratbox/include/libratbox_config.h
 libratbox/include/librb-config.h
 libratbox/include/stamp-h1
@@ -32,3 +31,5 @@ tools/convertilines
 tools/convertklines
 tools/mkpasswd
 tools/viconf
+syntax: regexp
+^include/serno\.h