diff --git a/scripts/runtests.sh b/scripts/runtests.sh
index 35259519..6e8e3780 100755
--- a/scripts/runtests.sh
+++ b/scripts/runtests.sh
@@ -41,7 +41,7 @@ timeout --foreground 60 sh -c "LANG=C.UTF-8 python3 -m subiquity.cmd.tui --autoi
 validate
 python3 scripts/check-yaml-fields.py .subiquity/subiquity-curtin-install.conf \
         debconf_selections.subiquity='"eek"'
-python3 scripts/check-yaml-fields.py <(python3 scripts/check-yaml-fields.py .subiquity/etc/cloud/cloud.cfg.d/installer.cfg datasource.None.userdata_raw) \
+python3 scripts/check-yaml-fields.py <(python3 scripts/check-yaml-fields.py .subiquity/etc/cloud/cloud.cfg.d/99-installer.cfg datasource.None.userdata_raw) \
         locale='"en_GB.UTF-8"'
 grep -q 'finish: subiquity/InstallProgress/install/postinstall/install_package1: SUCCESS: installing package1' \
      .subiquity/subiquity-debug.log
diff --git a/subiquity/models/subiquity.py b/subiquity/models/subiquity.py
index 51e0cd5a..58b71769 100644
--- a/subiquity/models/subiquity.py
+++ b/subiquity/models/subiquity.py
@@ -204,7 +204,7 @@ class SubiquityModel:
         # (mwhudson does not entirely know what the above means!)
         userdata = '#cloud-config\n' + yaml.dump(self._cloud_init_config())
         metadata = {'instance-id': str(uuid.uuid4())}
-        config = {
+        config = yaml.dump({
             'datasource_list': ["None"],
             'datasource': {
                 "None": {
@@ -212,9 +212,9 @@ class SubiquityModel:
                     'metadata': metadata,
                     },
                 },
-            }
+            })
         files = [
-            ('etc/cloud/cloud.cfg.d/installer.cfg', yaml.dump(config), 0o600),
+            ('etc/cloud/cloud.cfg.d/99-installer.cfg', config, 0o600),
             ('etc/cloud/ds-identify.cfg', 'policy: enabled\n', 0o644),
             ]
         if self.identity.hostname is not None: