diff --git a/apps/client/src/features/app-settings/panel/automations-panel/AutomationForm.tsx b/apps/client/src/features/app-settings/panel/automations-panel/AutomationForm.tsx
index a525bdef3..5ef01c891 100644
--- a/apps/client/src/features/app-settings/panel/automations-panel/AutomationForm.tsx
+++ b/apps/client/src/features/app-settings/panel/automations-panel/AutomationForm.tsx
@@ -230,13 +230,18 @@ export default function AutomationForm({ automation, onClose }: AutomationFormPr
               <div key={key} className={style.filterSection}>
                 <label>
                   Runtime data source
-                  <Select
-                    value={watch(`filters.${index}.field`)}
-                    onValueChange={(value: string | null) => {
+                  <Select<string | null>
+                    // need to normalize '' to null for the Select to show the placeholder
+                    value={watch(`filters.${index}.field`) || null}
+                    onValueChange={(value) => {
                       if (value === null) return;
                       setValue(`filters.${index}.field`, value, { shouldDirty: true });
                     }}
-                    options={fieldList.map(({ value, label }) => ({ value, label }))}
+                    options={fieldList.map(({ value, label }) => ({
+                      value,
+                      label,
+                      disabled: value === null,
+                    }))}
                     aria-label='Event field'
                   />
                   <Panel.Error>{errors.filters?.[index]?.field?.message}</Panel.Error>
@@ -288,7 +293,8 @@ export default function AutomationForm({ automation, onClose }: AutomationFormPr
       <div className={style.innerColumn}>
         <h3>Outputs</h3>
         <Info>
-          Automation outputs can be used to send data from Ontime to external software.
+          Automation outputs can be used to send data from Ontime to external software <br />
+          or to change properties of Ontime itself.
           <ExternalLink href={integrationsDocsUrl}>See the documentation for templates</ExternalLink>
         </Info>
 
diff --git a/apps/client/src/features/app-settings/panel/automations-panel/OntimeActionForm.tsx b/apps/client/src/features/app-settings/panel/automations-panel/OntimeActionForm.tsx
index a1379437b..269de44bb 100644
--- a/apps/client/src/features/app-settings/panel/automations-panel/OntimeActionForm.tsx
+++ b/apps/client/src/features/app-settings/panel/automations-panel/OntimeActionForm.tsx
@@ -97,15 +97,14 @@ export default function OntimeActionForm({
           <label>
             Visibility
             <Select
-              onValueChange={(value: boolean | 'untouched' | null) => {
-                if (value === null) return;
-                // we need to translate the undefined value to 'untouched'
-                const translatedValue = value === 'untouched' ? undefined : (value as boolean | undefined);
+              onValueChange={(value) => {
+                // we need to translate the null to undefined so it becomes 'untouched'
+                const translatedValue = value === null ? undefined : value;
                 setValue(`outputs.${index}.visible`, translatedValue, { shouldDirty: true });
               }}
-              value={watch(`outputs.${index}.visible`) === undefined ? 'untouched' : watch(`outputs.${index}.visible`)}
+              value={watch(`outputs.${index}.visible`)}
               options={[
-                { value: 'untouched', label: 'Untouched' },
+                { value: null, label: 'Untouched' },
                 { value: true, label: 'Show' },
                 { value: false, label: 'Hide' },
               ]}
@@ -118,10 +117,16 @@ export default function OntimeActionForm({
       {selectedAction === 'message-secondary' && (
         <label>
           Timer secondary source
-          <Select
-            onValueChange={(value: SecondarySource | null) => {
+          <Select<SecondarySource | 'null' | null>
+            onValueChange={(value) => {
+              // null -> no selection
               if (value === null) return;
-              setValue(`outputs.${index}.secondarySource`, value as SecondarySource, { shouldDirty: true });
+              // 'null' -> clear the secondary source
+              if (value === 'null') {
+                setValue(`outputs.${index}.secondarySource`, null, { shouldDirty: true });
+                return;
+              }
+              setValue(`outputs.${index}.secondarySource`, value, { shouldDirty: true });
             }}
             value={watch(`outputs.${index}.secondarySource`)}
             options={[
@@ -129,13 +134,14 @@ export default function OntimeActionForm({
               { value: 'aux1', label: 'Auxiliary timer 1' },
               { value: 'aux2', label: 'Auxiliary timer 2' },
               { value: 'aux3', label: 'Auxiliary timer 3' },
-              { value: 'external', label: 'External' },
-              { value: 'null', label: 'None' },
+              { value: 'secondary', label: 'Secondary' },
+              { value: 'null', label: 'None' }, // allow the user to clear the secondary source
             ]}
           />
           <Panel.Error>{rowErrors?.secondarySource?.message}</Panel.Error>
         </label>
       )}
+
       <div className={style.test}>{children}</div>
     </div>
   );
diff --git a/apps/client/src/features/app-settings/panel/automations-panel/automationUtils.ts b/apps/client/src/features/app-settings/panel/automations-panel/automationUtils.ts
index 7184a3d83..b83935970 100644
--- a/apps/client/src/features/app-settings/panel/automations-panel/automationUtils.ts
+++ b/apps/client/src/features/app-settings/panel/automations-panel/automationUtils.ts
@@ -27,6 +27,7 @@ export function isAutomation(automation: AutomationDTO | Automation): automation
 }
 
 const staticSelectProperties = [
+  { value: null, label: 'Select field' },
   { value: 'eventNow.id', label: 'ID' },
   { value: 'eventNow.title', label: 'Title' },
   { value: 'eventNow.cue', label: 'Cue' },
@@ -42,7 +43,7 @@ const staticNextSelectProperties = [
 ];
 
 type SelectableField = {
-  value: string; // string encodes path in runtime state object
+  value: string | null; // string encodes path in runtime state object
   label: string;
 };
 
diff --git a/apps/server/src/api-data/automation/automation.validation.ts b/apps/server/src/api-data/automation/automation.validation.ts
index 8d1b37191..5d92fdf03 100644
--- a/apps/server/src/api-data/automation/automation.validation.ts
+++ b/apps/server/src/api-data/automation/automation.validation.ts
@@ -124,8 +124,14 @@ export const validateTestPayload = [
   body('action').if(body('type').equals('ontime')).isString().trim(),
   body('text').if(body('type').equals('ontime')).optional().isString().trim(),
   body('time').if(body('type').equals('ontime')).optional().isString().trim(),
-  body('visible').if(body('type').equals('ontime')).optional().isString().trim(),
-  body('secondarySource').if(body('type').equals('ontime')).optional().isString().trim(),
+  body('visible').if(body('type').equals('ontime')).optional().isBoolean(),
+  // secondary source can be a enum case or null to clear it
+  body('secondarySource')
+    .if(body('type').equals('ontime'))
+    .optional({ nullable: true })
+    .if((value) => value !== null)
+    .isString()
+    .trim(),
 
   requestValidationFunction,
 ];
@@ -222,8 +228,16 @@ function parseOntimeAction(maybeOntimeAction: object): OntimeAction {
 
   if (maybeOntimeAction.action === 'message-secondary') {
     assert.hasKeys(maybeOntimeAction, ['secondarySource']);
-    assert.isString(maybeOntimeAction.secondarySource);
+    // null is used to clear the secondary source
+    if (maybeOntimeAction.secondarySource === null) {
+      return {
+        type: 'ontime',
+        action: 'message-secondary',
+        secondarySource: null,
+      };
+    }
 
+    assert.isString(maybeOntimeAction.secondarySource);
     return {
       type: 'ontime',
       action: 'message-secondary',
diff --git a/apps/server/src/services/message-service/message.service.ts b/apps/server/src/services/message-service/message.service.ts
index f739ca525..249790a6d 100644
--- a/apps/server/src/services/message-service/message.service.ts
+++ b/apps/server/src/services/message-service/message.service.ts
@@ -3,6 +3,7 @@ import { DeepPartial } from 'ts-essentials';
 
 import { throttle } from '../../utils/throttle.js';
 import type { StoreGetter, PublishFn } from '../../stores/EventStore.js';
+import { withoutUndefinedValues } from '../../../../../packages/utils/src/common/objectUtils.js';
 
 /**
  * Create a throttled version of the set function
@@ -42,7 +43,10 @@ export function patch(patch: DeepPartial<MessageState>): MessageState {
   // make a copy of the state in store
   const newState = { ...getState() };
 
-  if ('timer' in patch) newState.timer = { ...newState.timer, ...patch.timer };
+  if (patch.timer !== undefined) {
+    const sanitisedTimer = withoutUndefinedValues(patch.timer);
+    newState.timer = { ...newState.timer, ...sanitisedTimer };
+  }
   if ('secondary' in patch && patch.secondary !== undefined) newState.secondary = patch.secondary;
 
   throttledSet('message', newState);
diff --git a/packages/types/src/definitions/core/Automation.type.ts b/packages/types/src/definitions/core/Automation.type.ts
index 6e4fd6e2d..bf10843c4 100644
--- a/packages/types/src/definitions/core/Automation.type.ts
+++ b/packages/types/src/definitions/core/Automation.type.ts
@@ -98,6 +98,7 @@ export type OntimeAction =
       text?: string;
       visible?: boolean;
     }
+    // TODO: when setting a secondary source of type secondary we could specify a value to it
   | {
       type: 'ontime';
       action: OntimeMessageSecondary;
diff --git a/packages/utils/src/common/objectUtils.ts b/packages/utils/src/common/objectUtils.ts
index 882c56cb0..e646a8e02 100644
--- a/packages/utils/src/common/objectUtils.ts
+++ b/packages/utils/src/common/objectUtils.ts
@@ -17,6 +17,19 @@ export function getPropertyFromPath<T extends object>(path: string, obj: T): unk
   return result;
 }
 
+/**
+ * Whether an object is empty
+ */
 export function isObjectEmpty(obj: object): boolean {
   return Object.keys(obj).length === 0;
 }
+
+/**
+ * Removes a copy of the object without the properties which have undefined values
+ */
+export function withoutUndefinedValues<T extends Record<string, unknown>>(
+  obj: T,
+): { [K in keyof T]: Exclude<T[K], undefined> } {
+  Object.keys(obj).forEach((key) => obj[key] === undefined && delete obj[key]);
+  return obj as { [K in keyof T]: Exclude<T[K], undefined> };
+}