diff --git a/test-requirements.txt b/test-requirements.txt
index f9e67f3..b9cf601 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1 +1,4 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
 openstack-doc-tools>=0.18.1