diff --git a/build/environment.yml b/build/environment.yml
index df0319e..ee8f49c 100644
--- a/build/environment.yml
+++ b/build/environment.yml
@@ -7,6 +7,7 @@ dependencies:
   - cffi=1.12.3
   - ghp-import=0.5.5
   - jinja2=2.11.2
+  - markupsafe=2.0.1
   - jsonschema=3.2.0
   - pandoc=2.9.2
   - panflute=1.12.5