diff --git a/requirements.txt b/requirements.txt
index 34c77b30..f76dc88e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,6 +7,6 @@ raven>=5.23.0
 psutil>=3.0.0
 zipstream>=1.1.4
 typing>=3.5.3.0 # Otherwise yarl fails with python 3.4
-prompt-toolkit
+prompt-toolkit==1.0.15
 async-timeout<3.0.0 # pyup: ignore; 3.0 drops support for python 3.4