diff --git a/core/requirements.txt b/core/requirements.txt
index 48d2917..c3e4783 100644
--- a/core/requirements.txt
+++ b/core/requirements.txt
@@ -2,4 +2,5 @@
 # for version updates that isn't supported for contents inside the
 # Dockerfile.
 mailman==3.3.8
-mailman-hyperkitty==1.2.1
\ No newline at end of file
+mailman-hyperkitty==1.2.1
+importlib_resources<6.0