diff --git a/docs/requirements.txt b/docs/requirements.txt
index 848933a1d4..532825fc0d 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -4,6 +4,7 @@ sphinx==3.2.1
 sphinx-multiversion==0.2.4
 myst-parser==0.15.2
 myst-parser[linkify]==0.15.2
+simpleeval==0.9.11
 
 # recommonmark custom branch with evennia-specific fixes
 # git+https://github.com/evennia/recommonmark.git@evennia-mods#egg=recommonmark