diff --git a/docs/requirements.txt b/docs/requirements.txt
index 8ea4531..f0225f3 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -9,6 +9,7 @@ mike
 
 weasyprint==52.5
 mkdocs-with-pdf
+libpangocairo-1.0-0
 
 mkdocs-bootswatch