diff --git a/dom/base/MultipartBlobImpl.cpp b/dom/base/MultipartBlobImpl.cpp
index 0953101434def..1a517ad36844f 100644
--- a/dom/base/MultipartBlobImpl.cpp
+++ b/dom/base/MultipartBlobImpl.cpp
@@ -335,7 +335,7 @@ MultipartBlobImpl::InitializeChromeFile(Blob& aBlob,
     return;
   }
 
-  MOZ_ASSERT(nsContentUtils::IsCallerChrome());
+  MOZ_ASSERT(nsContentUtils::ThreadsafeIsCallerChrome());
 
   mName = aBag.mName;
   mContentType = aBag.mType;