diff --git a/netwerk/streamconv/converters/nsIndexedToHTML.cpp b/netwerk/streamconv/converters/nsIndexedToHTML.cpp
index a7131faba248..fbc1df57a0a7 100644
--- a/netwerk/streamconv/converters/nsIndexedToHTML.cpp
+++ b/netwerk/streamconv/converters/nsIndexedToHTML.cpp
@@ -549,7 +549,7 @@ nsIndexedToHTML::OnIndexAvailable(nsIRequest *aRequest,
     PRInt64 size;
     aIndex->GetSize(&size);
     
-    if (nsUint64(size) != LL_MAXUINT &&
+    if (nsUint64(PRUint64(size)) != LL_MAXUINT &&
         type != nsIDirIndex::TYPE_DIRECTORY &&
         type != nsIDirIndex::TYPE_SYMLINK) {
         nsAutoString  sizeString;