diff --git a/doc/source/conf.py b/doc/source/conf.py
index 3631de159c..e992e170d6 100755
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -22,7 +22,8 @@ sys.path.insert(0, os.path.abspath('../..'))
 extensions = [
     'sphinx.ext.autodoc',
     'openstackdocstheme',
-    'oslosphinx'
+    'oslosphinx',
+    'sphinxcontrib.blockdiag'
 ]
 
 # autodoc generation is a bit aggressive and a nuisance when doing heavy
diff --git a/test-requirements.txt b/test-requirements.txt
index b32d08c1f7..2363612449 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,4 +1,5 @@
 sphinx>=1.5.1,!=1.6.1 # BSD
+sphinxcontrib-blockdiag>=1.1.0
 oslosphinx>=4.7.0 # Apache-2.0
 pbr>=3.0.0 # Apache-2.0
-openstackdocstheme>=1.16.0 # Apache-2.0
\ No newline at end of file
+openstackdocstheme>=1.16.0 # Apache-2.0