How to set some datas in Vuex store from an API call

So, I don't get how to set an array of data fetched by API in Vuex.

This is what I'm trying

/* store/modules/galleries.js */

// mutations
const mutations = {
    SET_GALLERIES(state, galleries) {
        state.galleries = galleries;
    }
};

// actions
const actions = {
    fetchAllGalleries({ commit }) {
        Vue.prototype.$oauth.request('/galleries')
            .then(galleries => {
                console.log(galleries) // [{...}, {...}, ...]
                commit('SET_GALLERIES', galleries);
            });
     }
}

/* myComponent.vue */

computed: {
    ...mapState('galleries', ['galleries'])
},
mounted() {
    this.$store.dispatch('galleries/fetchAllGalleries');
}

But somehow my state.galleries always stay at his original state even though the commit is called.

What could be the error coming from?