diff --git a/requirements.txt b/requirements.txt
index 970c5994..8f13ef5d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,5 +7,5 @@ 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
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