diff --git a/mozilla/modules/libimg/src/ilNetReader.cpp b/mozilla/modules/libimg/src/ilNetReader.cpp
index f5c6c07214d..c1253b1659b 100644
--- a/mozilla/modules/libimg/src/ilNetReader.cpp
+++ b/mozilla/modules/libimg/src/ilNetReader.cpp
@@ -68,7 +68,7 @@ NetReaderImpl::~NetReaderImpl()
 {
 }
 
-NS_IMPL_ISUPPORTS(NetReaderImpl, kINetReaderIID)
+NS_IMPL_THREADSAFE_ISUPPORTS(NetReaderImpl, kINetReaderIID)
 
 NS_IMETHODIMP
 NetReaderImpl::WriteReady(PRUint32* max_read)