diff --git a/requirements.txt b/requirements.txt
index 682e868..169f860 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -90,6 +90,7 @@ sphinxcontrib-bibtex==2.6.2
 sphinxcontrib-devhelp==1.0.6
 sphinxcontrib-htmlhelp==2.0.5
 sphinxcontrib-jsmath==1.0.1
+sphinxcontrib-mermaid==0.9.2
 sphinxcontrib-qthelp==1.0.7
 sphinxcontrib-serializinghtml==1.1.10
 SQLAlchemy==2.0.31