diff --git a/lib/spack/docs/requirements.txt b/lib/spack/docs/requirements.txt
index 08cd3ea4eb6..8a5d3a521b1 100644
--- a/lib/spack/docs/requirements.txt
+++ b/lib/spack/docs/requirements.txt
@@ -8,3 +8,4 @@ python-levenshtein
 # Restrict to docutils <0.17 to workaround a list rendering issue in sphinx.
 # https://stackoverflow.com/questions/67542699
 docutils <0.17
+pygments <2.13