diff --git a/docs/requirements.txt b/docs/requirements.txt
index e1b2384bb0..1201daa1a3 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -8,4 +8,5 @@ sphinxcontrib-blockdiag>=1.5.5, <2.0.0
 sphinxcontrib-seqdiag>=0.8.5, <2.0.0
 sphinxcontrib-actdiag>=0.8.5, <2.0.0
 sphinxcontrib-nwdiag>=0.9.5, <2.0.0
+nwdiag==1.0.4
 recommonmark