diff --git a/netwerk/protocol/file/nsFileChannel.cpp b/netwerk/protocol/file/nsFileChannel.cpp
index ba30ed9a6394..133a60ae0f48 100644
--- a/netwerk/protocol/file/nsFileChannel.cpp
+++ b/netwerk/protocol/file/nsFileChannel.cpp
@@ -312,10 +312,14 @@ nsFileChannel::MakeFileInputStream(nsIFile *file,
   bool isDir;
   nsresult rv = file->IsDirectory(&isDir);
   if (NS_FAILED(rv)) {
-    // canonicalize error message
-    if (rv == NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)
-      rv = NS_ERROR_FILE_NOT_FOUND;
-    return rv;
+    if (NS_ERROR_FILE_NOT_FOUND == rv ||
+        NS_ERROR_FILE_TARGET_DOES_NOT_EXIST == rv) {
+      // We don't return "Not Found" errors here. Since we could not find
+      // the file, it's not a directory anyway.
+      isDir = false;
+    } else {
+      return rv;
+    }
   }
 
   if (isDir) {
@@ -323,7 +327,8 @@ nsFileChannel::MakeFileInputStream(nsIFile *file,
     if (NS_SUCCEEDED(rv) && !HasContentTypeHint())
       contentType.AssignLiteral(APPLICATION_HTTP_INDEX_FORMAT);
   } else {
-    rv = NS_NewLocalFileInputStream(getter_AddRefs(stream), file);
+    rv = NS_NewLocalFileInputStream(getter_AddRefs(stream), file, -1, -1,
+                                    nsIFileInputStream::DEFER_OPEN);
     if (NS_SUCCEEDED(rv) && !HasContentTypeHint()) {
       // Use file extension to infer content type
       nsCOMPtr<nsIMIMEService> mime = do_GetService("@mozilla.org/mime;1", &rv);
@@ -407,8 +412,14 @@ nsFileChannel::OpenContentStream(bool async, nsIInputStream **result,
     if (ContentLength64() < 0) {
       PRInt64 size;
       rv = file->GetFileSize(&size);
-      if (NS_FAILED(rv))
-        return rv;
+      if (NS_FAILED(rv)) {
+        if (NS_ERROR_FILE_NOT_FOUND == rv ||
+            NS_ERROR_FILE_TARGET_DOES_NOT_EXIST == rv) {
+          size = 0;
+        } else {
+          return rv;
+        }
+      }
       SetContentLength64(size);
     }
     if (!contentType.IsEmpty())