diff --git a/doc/requirements.txt b/doc/requirements.txt
index 22777b75d7..ff68f5f5c1 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,6 +1,5 @@
 sphinx>=2.1.1 # BSD
 sphinxcontrib-httpdomain>=1.3.0 # BSD
-sphinxcontrib-blockdiag>=1.5.4 # BSD
 reno>=3.1.0 # Apache-2.0
 os-api-ref>=1.4.0 # Apache-2.0
 openstackdocstheme>=2.2.1 # Apache-2.0