diff --git a/build/gen_setting_pm.pl b/build/gen_setting_pm.pl
index aade9de40d9..c8175b863f6 100644
--- a/build/gen_setting_pm.pl
+++ b/build/gen_setting_pm.pl
@@ -30,6 +30,7 @@
 print <<"END_SETTING";
 # Need to use all built-in classes, to import their exports.
 END_SETTING
+s/\\/\//g for @classes;
 print join('', map {
     my $colon_form = $_;
     $colon_form =~ s/[\/\\]/::/g;