diff --git a/mozilla/netwerk/test/TestOpen.cpp b/mozilla/netwerk/test/TestOpen.cpp
index 045a409ac6c..1643a17943b 100644
--- a/mozilla/netwerk/test/TestOpen.cpp
+++ b/mozilla/netwerk/test/TestOpen.cpp
@@ -86,7 +86,7 @@ main(int argc, char **argv)
 
     PRUint32 read;
     while (NS_SUCCEEDED(stream->Read(buf, sizeof(buf), &read)) && read) {
-      fwrite(buf, 1, sizeof(buf), outfile);
+      fwrite(buf, 1, read, outfile);
     }
     printf("Done\n");