diff --git a/xpcom/io/nsIBaseStream.idl b/xpcom/io/nsIBaseStream.idl
index b7076a8a5016..52800b291e3c 100644
--- a/xpcom/io/nsIBaseStream.idl
+++ b/xpcom/io/nsIBaseStream.idl
@@ -41,5 +41,7 @@ interface nsIBaseStream : nsISupports
 #define NS_BASE_STREAM_BAD_CONVERSION NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_BASE, 6)
 
 #define NS_BASE_STREAM_WOULD_BLOCK    NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_BASE, 7)
+
+#define NS_BASE_STREAM_FULL           NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_BASE, 8)
 //@}
 %}