diff --git a/dom/indexedDB/IDBObjectStore.cpp b/dom/indexedDB/IDBObjectStore.cpp
index 0aa9d06649..e0e3db0ed0 100644
--- a/dom/indexedDB/IDBObjectStore.cpp
+++ b/dom/indexedDB/IDBObjectStore.cpp
@@ -68,7 +68,9 @@ struct IDBObjectStore::StructuredCloneWriteInfo
   uint64_t mOffsetToKeyProp;
 
   explicit StructuredCloneWriteInfo(IDBDatabase* aDatabase)
-    : mCloneBuffer(JS::StructuredCloneScope::DifferentProcessForIndexedDB, nullptr,
+    // DifferentProcessForIndexedDB is a read-only compatibility mode. New
+    // records must use the durable, cross-process serialization format.
+    : mCloneBuffer(JS::StructuredCloneScope::DifferentProcess, nullptr,
                    nullptr)
     , mDatabase(aDatabase)
     , mOffsetToKeyProp(0)
diff --git a/dom/indexedDB/test/unit/test_cache_record_roundtrip.js b/dom/indexedDB/test/unit/test_cache_record_roundtrip.js
new file mode 100644
index 0000000000..7fa7c283d7
--- /dev/null
+++ b/dom/indexedDB/test/unit/test_cache_record_roundtrip.js
@@ -0,0 +1,49 @@
+/**
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+var testGenerator = testSteps();
+
+function* testSteps() {
+  const name = "cache-record-roundtrip";
+  let request = indexedDB.open(name, 1);
+  request.onerror = errorHandler;
+  request.onupgradeneeded = event => {
+    event.target.result.createObjectStore("cache", {keyPath: "key"});
+  };
+  request.onsuccess = grabEventAndContinueHandler;
+  let event = yield undefined;
+  let db = event.target.result;
+  let transaction = db.transaction("cache", "readwrite");
+  transaction.onabort = errorHandler;
+  transaction.oncomplete = grabEventAndContinueHandler;
+  let store = transaction.objectStore("cache");
+  store.put({key: "text", value: "compiled filter data"});
+  store.put({key: "bytes", value: new Uint8Array([0, 1, 127, 255])});
+  store.put({key: "empty", value: new ArrayBuffer(0)});
+  yield undefined;
+  db.close();
+
+  // Reopen after committing: test the serialized database records, rather than
+  // just observing successful writes or values still held by the caller.
+  request = indexedDB.open(name, 1);
+  request.onerror = errorHandler;
+  request.onsuccess = grabEventAndContinueHandler;
+  event = yield undefined;
+  db = event.target.result;
+  request = db.transaction("cache").objectStore("cache").getAll();
+  request.onerror = errorHandler;
+  request.onsuccess = grabEventAndContinueHandler;
+  event = yield undefined;
+  let records = event.target.result;
+  is(records.length, 3, "All committed records are readable");
+  is(records[0].key, "bytes", "Records retain their keys");
+  ok(records[0].value instanceof Uint8Array, "Typed array type survives storage");
+  is(Array.from(records[0].value).join(), "0,1,127,255", "Bytes survive storage");
+  is(records[1].value.byteLength, 0, "Empty buffers survive storage");
+  is(records[2].value, "compiled filter data", "Strings survive storage");
+  db.close();
+  finishTest();
+  yield undefined;
+}
diff --git a/dom/indexedDB/test/unit/xpcshell-shared.ini b/dom/indexedDB/test/unit/xpcshell-shared.ini
index 05359097bd..8a4db0f4f9 100644
--- a/dom/indexedDB/test/unit/xpcshell-shared.ini
+++ b/dom/indexedDB/test/unit/xpcshell-shared.ini
@@ -10,6 +10,7 @@
 [test_autoIncrement.js]
 [test_autoIncrement_indexes.js]
 [test_blocked_order.js]
+[test_cache_record_roundtrip.js]
 [test_clear.js]
 [test_complex_keyPaths.js]
 [test_count.js]