diff --git a/ext/bg/js/database.js b/ext/bg/js/database.js
index 9eed8ea3..45ba3d08 100644
--- a/ext/bg/js/database.js
+++ b/ext/bg/js/database.js
@@ -224,7 +224,53 @@ class Database {
             await this.db.kanji.bulkAdd(rows);
         };
 
-        await zipLoadDb(archive, indexLoaded, termsLoaded, kanjiLoaded);
+        await Database.importDictionaryZip(archive, indexLoaded, termsLoaded, kanjiLoaded);
         return summary;
     }
+
+    static async importDictionaryZip(archive, indexLoaded, termsLoaded, kanjiLoaded) {
+        const files = (await JSZip.loadAsync(archive)).files;
+
+        const indexFile = files['index.json'];
+        if (!indexFile) {
+            throw 'no dictionary index found in archive';
+        }
+
+        const index = JSON.parse(await indexFile.async('string'));
+        if (!index.title || !index.version || !index.revision) {
+            throw 'unrecognized dictionary format';
+        }
+
+        await indexLoaded(
+            index.title,
+            index.version,
+            index.revision,
+            index.tagMeta || {},
+            index.termBanks > 0,
+            index.kanjiBanks > 0
+        );
+
+        const banksTotal = index.termBanks + index.kanjiBanks;
+        let banksLoaded = 0;
+
+        for (let i = 1; i <= index.termBanks; ++i) {
+            const bankFile = files[`term_bank_${i}.json`];
+            if (bankFile) {
+                const bank = JSON.parse(await bankFile.async('string'));
+                await termsLoaded(index.title, bank, banksTotal, banksLoaded++);
+            } else {
+                throw 'missing term bank file';
+            }
+        }
+
+        for (let i = 1; i <= index.kanjiBanks; ++i) {
+            const bankFile = files[`kanji_bank_${i}.json`];
+            if (bankFile) {
+                const bank = JSON.parse(await bankFile.async('string'));
+                await kanjiLoaded(index.title, bank, banksTotal, banksLoaded++);
+            } else {
+                throw 'missing kanji bank file';
+            }
+        }
+    }
 }
diff --git a/ext/bg/js/util.js b/ext/bg/js/util.js
index b39b4b2f..1954e83b 100644
--- a/ext/bg/js/util.js
+++ b/ext/bg/js/util.js
@@ -455,70 +455,6 @@ function jsonLoadInt(url) {
     return jsonLoad(chrome.extension.getURL(url));
 }
 
-/*
- * Zip
- */
-
-function zipLoadDb(archive, indexLoaded, termsLoaded, kanjiLoaded) {
-    return JSZip.loadAsync(archive).then(files => files.files).then(files => {
-        const indexFile = files['index.json'];
-        if (!indexFile) {
-            return Promise.reject('no dictionary index found in archive');
-        }
-
-        return indexFile.async('string').then(indexJson => {
-            const index = JSON.parse(indexJson);
-            if (!index.title || !index.version || !index.revision) {
-                return Promise.reject('unrecognized dictionary format');
-            }
-
-            return indexLoaded(
-                index.title,
-                index.version,
-                index.revision,
-                index.tagMeta || {},
-                index.termBanks > 0,
-                index.kanjiBanks > 0
-            ).then(() => index);
-        }).then(index => {
-            const loaders = [];
-            const banksTotal = index.termBanks + index.kanjiBanks;
-            let banksLoaded = 0;
-
-            for (let i = 1; i <= index.termBanks; ++i) {
-                const bankFile = files[`term_bank_${i}.json`];
-                if (!bankFile) {
-                    return Promise.reject('missing term bank file');
-                }
-
-                loaders.push(() => bankFile.async('string').then(bankJson => {
-                    const bank = JSON.parse(bankJson);
-                    return termsLoaded(index.title, bank, banksTotal, banksLoaded++);
-                }));
-            }
-
-            for (let i = 1; i <= index.kanjiBanks; ++i) {
-                const bankFile = files[`kanji_bank_${i}.json`];
-                if (!bankFile) {
-                    return Promise.reject('missing kanji bank file');
-                }
-
-                loaders.push(() => bankFile.async('string').then(bankJson => {
-                    const bank = JSON.parse(bankJson);
-                    return kanjiLoaded(index.title, bank, banksTotal, banksLoaded++);
-                }));
-            }
-
-            let chain = Promise.resolve();
-            for (const loader of loaders) {
-                chain = chain.then(loader);
-            }
-
-            return chain;
-        });
-    });
-}
-
 /*
  * Helpers
  */