Issue #5206 has been updated by usa (Usaku NAKAMURA). Status changed from Closed to Assigned I think that it is good for warning, but isn't only the time of -w option being specified? ---------------------------------------- Feature #5206: ruby -K should warn https://bugs.ruby-lang.org/issues/5206#change-27743 Author: drbrain (Eric Hodel) Status: Assigned Priority: Normal Assignee: naruse (Yui NARUSE) Category: core Target version: When ruby is run with -K it changes the default encoding of all files even when that may be incompatible with the source. If many libraries are used -K may cause incorrect behavior. Now that we have the "coding:" magic comment ruby should warn if the -K flag is used and suggest that "coding:" magic comment be used instead. -- http://bugs.ruby-lang.org/