diff --git a/test/testdrive/github-6942.td b/test/testdrive/github-6942.td
index f9993a4c9c7af..e1c50d0a0b07b 100644
--- a/test/testdrive/github-6942.td
+++ b/test/testdrive/github-6942.td
@@ -7,6 +7,8 @@
 # the Business Source License, use of this software will be governed
 # by the Apache License, Version 2.0.
 
+$ set-arg-default default-storage-size=1
+
 > DROP CLUSTER IF EXISTS gh_6942_cluster CASCADE;
 > CREATE CLUSTER gh_6942_cluster SIZE '${arg.default-storage-size}', REPLICATION FACTOR 1;
 
diff --git a/test/testdrive/webhook.td b/test/testdrive/webhook.td
index dbbf8ac1981da..b3eaf1b0fbe5b 100644
--- a/test/testdrive/webhook.td
+++ b/test/testdrive/webhook.td
@@ -8,6 +8,7 @@
 # by the Apache License, Version 2.0.
 
 $ set-arg-default replicas=1
+$ set-arg-default default-storage-size=1
 
 # Exercises Webhook sources.