If you run: rake gemspec:validate --trace
It throws this error:
The same error occurs with both commit e8e0756 (0.4.0dev) and tag 0.3.0.
It might be this bug in Jeweler itself:
It definitely looks like a bug in Jeweler... I'll keep an eye on it.
Version is now specified in lib/glyph.rb.
* Closes #151.