diff --git a/src/content/actions/setting.js b/src/content/actions/setting.js
index 353dd24..0238c71 100644
--- a/src/content/actions/setting.js
+++ b/src/content/actions/setting.js
@@ -2,21 +2,20 @@ import actions from 'content/actions';
 import * as keyUtils from 'shared/utils/keys';
 
 const set = (value) => {
-  let maps = new Map();
+  let entries = [];
   if (value.keymaps) {
-    let entries = Object.entries(value.keymaps).map((entry) => {
+    entries = Object.entries(value.keymaps).map((entry) => {
       return [
         keyUtils.fromMapKeys(entry[0]),
         entry[1],
       ];
     });
-    maps = new Map(entries);
   }
 
   return {
     type: actions.SETTING_SET,
     value: Object.assign({}, value, {
-      keymaps: maps,
+      keymaps: entries,
     })
   };
 };
diff --git a/src/content/components/common/keymapper.js b/src/content/components/common/keymapper.js
index 0abbc91..fb8fabe 100644
--- a/src/content/components/common/keymapper.js
+++ b/src/content/components/common/keymapper.js
@@ -25,7 +25,7 @@ export default class KeymapperComponent {
 
     let state = this.store.getState();
     let input = state.input;
-    let keymaps = state.setting.keymaps;
+    let keymaps = new Map(state.setting.keymaps);
 
     let matched = Array.from(keymaps.keys()).filter((mapping) => {
       return mapStartsWith(mapping, input.keys);
diff --git a/src/content/reducers/setting.js b/src/content/reducers/setting.js
index a54f5a3..a23027f 100644
--- a/src/content/reducers/setting.js
+++ b/src/content/reducers/setting.js
@@ -1,7 +1,8 @@
 import actions from 'content/actions';
 
 const defaultState = {
-  keymaps: new Map(),
+  // keymaps is and arrays of key-binding pairs, which is entries of Map
+  keymaps: [],
 };
 
 export default function reducer(state = defaultState, action = {}) {
diff --git a/test/content/actions/setting.test.js b/test/content/actions/setting.test.js
index 0228fea..1248edf 100644
--- a/test/content/actions/setting.test.js
+++ b/test/content/actions/setting.test.js
@@ -20,8 +20,8 @@ describe("setting actions", () => {
         }
       });
       let keymaps = action.value.keymaps;
-
-      expect(action.value.keymaps).to.have.deep.all.keys(
+      let map = new Map(keymaps);
+      expect(map).to.have.deep.all.keys(
         [
           [{ key: 'd', shiftKey: false, ctrlKey: false, altKey: false, metaKey: false },
            { key: 'd', shiftKey: false, ctrlKey: false, altKey: false, metaKey: false }],