diff --git a/lib/thwait/thwait.gemspec b/lib/thwait/thwait.gemspec
index 2aa31bdf018e40..fc03942abaea3c 100644
--- a/lib/thwait/thwait.gemspec
+++ b/lib/thwait/thwait.gemspec
@@ -1,6 +1,7 @@
 begin
   require_relative "lib/thwait/version"
 rescue LoadError
+  # for Ruby core repository
   require_relative "version"
 end