diff --git a/requirements.txt b/requirements.txt
index 1627cca9e..fccd7c4ce 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -20,6 +20,7 @@ PySocks==1.6.7
 PyYAML==4.2b1
 requests==2.22.0
 six==1.12.0
+subprocess32==3.5.4; python_version < '3.2'
 texttable==1.6.2
 urllib3==1.24.2; python_version == '3.3'
 websocket-client==0.32.0