diff --git a/antsibull-nox.toml b/antsibull-nox.toml
index 410f37884e..d4ec6bdd46 100644
--- a/antsibull-nox.toml
+++ b/antsibull-nox.toml
@@ -12,6 +12,10 @@
 # community.crypto's main branch needs ansible-core >= 2.17
 "community.crypto" = "git+https://github.com/ansible-collections/community.crypto.git,stable-2"
 
+[collection_sources_per_ansible.'2.17']
+# The Ubuntu 20.04 image from ansible-core 2.17 has an old enough cryptography that won't work with community.crypto's main branch.
+"community.crypto" = "git+https://github.com/ansible-collections/community.crypto.git,stable-2"
+
 [vcs]
 vcs = "git"
 development_branch = "main"