diff --git a/modules/libjar/zipwriter/src/nsZipWriter.cpp b/modules/libjar/zipwriter/src/nsZipWriter.cpp
index 57fe1cab1a07..c2ebdd9a65d6 100644
--- a/modules/libjar/zipwriter/src/nsZipWriter.cpp
+++ b/modules/libjar/zipwriter/src/nsZipWriter.cpp
@@ -301,7 +301,7 @@ NS_IMETHODIMP nsZipWriter::Open(nsIFile *aFile, PRInt32 aIoFlags)
         return rv;
     }
 
-    rv = NS_NewBufferedOutputStream(getter_AddRefs(mStream), stream, 3 * 1024 * 1024);
+    rv = NS_NewBufferedOutputStream(getter_AddRefs(mStream), stream, 64 * 1024);
     if (NS_FAILED(rv)) {
         stream->Close();
         mHeaders.Clear();