diff --git a/docs/requirements.txt b/docs/requirements.txt
index 1201daa1a..2dad64365 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -8,5 +8,8 @@ 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
+blockdiag>=1.5.4, <2.0.0
+seqdiag>=0.9.6, <2.0.0
+actdiag>=0.5.4, <2.0.0
+nwdiag>=1.0.4, <2.0.0
 recommonmark