diff --git a/ci/config.sh b/ci/config.sh
index 508d454f883f8a3d346ddb33672230100fb04993..b1f5fb3370d49db7e9d54e664e6746af9e8a9cbd 100644
--- a/ci/config.sh
+++ b/ci/config.sh
@@ -103,6 +103,7 @@ extra_package servant 0.18.3
 extra_package hgmp
 extra_package Agda 2.6.1.3
 extra_package mmark
+extra_package doctest
 
 # Build-tool packages
 build_tool_package alex