Using Vuex getters inside a supply

Hi, I'm having a hard time wrapping my head around the way supply cache is used.

I'm injecting the store (composed with injectSupply(storeOptions, supplyCache)), but when I try to use it in my supply with this.$store I get two keys :

this.$store.default which is the store I want to use,
and this.$store.supplyCache.

Therefore I can't use mapgetters and all. Is there a right way to access store getters from the supply? When I'm trying to launch a subscription depending on Vuex store data it seems that this.$store.default is undefined on first run so it makes the app crash.