diff --git a/openappstack/__main__.py b/openappstack/__main__.py
index 9efad5bc2ff309f7419f487c934fb5b4e9e0d792..2393029622c070a726ca3e1e47e931c99052a3f4 100755
--- a/openappstack/__main__.py
+++ b/openappstack/__main__.py
@@ -30,6 +30,7 @@ ALL_TESTS = ['behave']
 
 # We're limiting to 56, because we use subdomains, the longest of which
 # is 7 characters (`office.`). Max CN length is 63 characters.
+# See https://github.com/jetstack/cert-manager/issues/2794 for details.
 MAX_DOMAIN_LENGTH = 56