diff --git a/pupy/requirements.txt b/pupy/requirements.txt
index 97b4dc917..51f226ecf 100644
--- a/pupy/requirements.txt
+++ b/pupy/requirements.txt
@@ -11,7 +11,7 @@ psutil
 netifaces
 pylzma
 colorama
-mss
+mss=4.0.3
 pyOpenSSL
 scapy
 https://github.com/CoreSecurity/impacket/archive/master.zip