diff --git a/requirements-doc.txt b/requirements-doc.txt
index 2a9441c..b8d8b41 100644
--- a/requirements-doc.txt
+++ b/requirements-doc.txt
@@ -1,5 +1,5 @@
 sphinx==5.3.0
-docutils=0.17.1
+docutils==0.17.1
 sphinxcontrib-blockdiag
 openpyxl
 pandas