diff --git a/requirements.txt b/requirements.txt
index eb984cd9eed..78f062adc06 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -39,5 +39,6 @@ oslo.serialization>=1.10.0 # Apache-2.0
 oslo.service>=0.12.0 # Apache-2.0
 oslo.utils>=2.8.0 # Apache-2.0
 oslo.versionedobjects>=0.13.0
+ovs>=2.4.0;python_version=='2.7'        # Apache-2.0
 
 python-novaclient!=2.33.0,>=2.29.0