diff --git a/background/background.js b/background/background.js
index 95679239..24631a52 100644
--- a/background/background.js
+++ b/background/background.js
@@ -155,6 +155,12 @@ addAPI(/** @namespace API */ {
     getValues: () => prefs.__values, // will be deepCopy'd by apiHandler
     set: prefs.set,
   },
+
+  /**
+   * Storage for big items that may exceed 8kB limit of chrome.storage.sync.
+   * To make an item syncable register it with uuidIndex.addCustomId.
+   */
+  prefsDb: db.open(prefs.STORAGE_KEY),
 });
 
 //#endregion
diff --git a/background/common.js b/background/common.js
index 9eb6ba1e..ef1c0ffd 100644
--- a/background/common.js
+++ b/background/common.js
@@ -11,11 +11,9 @@ bgReady.all = new Promise(r => (bgReady._resolveAll = r));
 
 const uuidIndex = Object.assign(new Map(), {
   custom: {},
-  addCustomId(obj, setter) {
-    Object.defineProperty(uuidIndex.custom, obj.id, {
-      get: () => obj,
-      set: setter,
-    });
+  /** `obj` must have a unique `id`, a UUIDv4 `_id`, and Date.now() for `_rev`. */
+  addCustomId(obj, {get = () => obj, set}) {
+    Object.defineProperty(uuidIndex.custom, obj.id, {get, set});
   },
 });
 
diff --git a/background/style-manager.js b/background/style-manager.js
index 3d4f4d9a..b976ef20 100644
--- a/background/style-manager.js
+++ b/background/style-manager.js
@@ -73,7 +73,7 @@ const styleMan = (() => {
     _id: `${chrome.runtime.id}-${INJ_ORDER}`,
     _rev: 0,
   };
-  uuidIndex.addCustomId(orderWrap, setOrder);
+  uuidIndex.addCustomId(orderWrap, {set: setOrder});
   /** @type {Promise|boolean} will be `true` to avoid wasting a microtask tick on each `await` */
   let ready = init();
 
@@ -505,7 +505,7 @@ const styleMan = (() => {
   }
 
   async function init() {
-    const orderPromise = db.open(prefs.STORAGE_KEY).get(INJ_ORDER);
+    const orderPromise = API.prefsDb.get(INJ_ORDER);
     const styles = await db.styles.getAll() || [];
     const updated = await Promise.all(styles.map(fixKnownProblems).filter(Boolean));
     if (updated.length) {
@@ -738,7 +738,7 @@ const styleMan = (() => {
       msg.broadcast({method: 'styleSort', order});
     }
     if (store) {
-      await db.open(prefs.STORAGE_KEY).put(orderWrap);
+      await API.prefsDb.put(orderWrap);
     }
     if (sync) {
       API.sync.putDoc(orderWrap);