diff --git a/requirements.txt b/requirements.txt
index 9d750eb..d8ea987 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 requests==2.24.0
 
 # testing
-mock==4.0.3
+mock==3.0.5
 httpretty==1.1.4
 coveralls==1.11.1
 coverage==5.2.1