Bug (Maybe) - Support Gem Zenith II and Despair

Hello GGG,

Despite the fact that Zenith II support gem describes that 25% of the mana cost is recovered for spells, this ability does not work with despair spell when Doedre's Undoing is used.

However the part concerning the damages is correctly observed. (+30% damages over 90% of mana)

The spell setup
Skill gem : Despair
Support Gem : Doedre's Undoing
Support Gem : Zenith II
Support Gem : Spell Cascade
Support Gem : Rakiata's Flow
Support Gem : Tul's Stillness

Ty