diff --git a/changes/noissue.1.fix.rst b/changes/noissue.1.fix.rst
new file mode 100644
index 00000000..a407fe6f
--- /dev/null
+++ b/changes/noissue.1.fix.rst
@@ -0,0 +1 @@
+Dev: Added missing dependency defusedxml (used by sphinx).
diff --git a/minimum-constraints-develop.txt b/minimum-constraints-develop.txt
index fbf5e822..ec21f414 100644
--- a/minimum-constraints-develop.txt
+++ b/minimum-constraints-develop.txt
@@ -113,6 +113,7 @@ cachetools==5.3.2  # used by tox since its 4.0.0
 clint==0.5.1
 configparser==4.0.2
 contextlib2==0.6.0
+defusedxml==0.7.1  # used by Sphinx
 distlib==0.3.7
 filelock==3.13.1
 gitdb2==2.0.0