diff --git a/dom/file/Blob.h b/dom/file/Blob.h
index cca88cba40a0..72b74ed9fb3f 100644
--- a/dom/file/Blob.h
+++ b/dom/file/Blob.h
@@ -41,7 +41,7 @@ class Blob : public nsSupportsWeakReference, public nsWrapperCache {
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(Blob)
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_DOM_BLOB_IID)
 
-  typedef OwningArrayBufferViewOrArrayBufferOrBlobOrUSVString BlobPart;
+  using BlobPart = OwningArrayBufferViewOrArrayBufferOrBlobOrUSVString;
 
   // This creates a Blob or a File based on the type of BlobImpl.
   static Blob* Create(nsIGlobalObject* aGlobal, BlobImpl* aImpl);
diff --git a/dom/file/MemoryBlobImpl.cpp b/dom/file/MemoryBlobImpl.cpp
index a63f96cfdd50..0e5b60f19621 100644
--- a/dom/file/MemoryBlobImpl.cpp
+++ b/dom/file/MemoryBlobImpl.cpp
@@ -108,7 +108,7 @@ class MemoryBlobImplDataOwnerMemoryReporter final : public nsIMemoryReporter {
 
   NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
                             nsISupports* aData, bool aAnonymize) override {
-    typedef MemoryBlobImpl::DataOwner DataOwner;
+    using DataOwner = MemoryBlobImpl::DataOwner;
 
     StaticMutexAutoLock lock(DataOwner::sDataOwnerMutex);
 
diff --git a/dom/file/MemoryBlobImpl.h b/dom/file/MemoryBlobImpl.h
index dfe5ae2e65da..ffe05e244437 100644
--- a/dom/file/MemoryBlobImpl.h
+++ b/dom/file/MemoryBlobImpl.h
@@ -108,7 +108,7 @@ class MemoryBlobImpl final : public BaseBlobImpl {
                                  public nsISeekableStream,
                                  public nsIIPCSerializableInputStream,
                                  public nsICloneableInputStream {
-    typedef MemoryBlobImpl::DataOwner DataOwner;
+    using DataOwner = MemoryBlobImpl::DataOwner;
 
    public:
     static nsresult Create(DataOwner* aDataOwner, uint32_t aStart,