diff --git a/apps/server/src/api-integration/integration.controller.ts b/apps/server/src/api-integration/integration.controller.ts
index 57a8dc7f7..662f1c35d 100644
--- a/apps/server/src/api-integration/integration.controller.ts
+++ b/apps/server/src/api-integration/integration.controller.ts
@@ -47,8 +47,8 @@ const actionHandlers: Record<string, ActionHandler> = {
       if (typeof property !== 'string' || value === undefined) {
         throw new Error('Invalid property or value');
       }
-      // all custom fields keys are lowercase
-      const newObjectProperty = parseProperty(property.toLowerCase(), value);
+
+      const newObjectProperty = parseProperty(property, value);
 
       if (patchEvent.custom && newObjectProperty.custom) {
         Object.assign(patchEvent.custom, newObjectProperty.custom);
diff --git a/apps/server/src/api-integration/integration.utils.ts b/apps/server/src/api-integration/integration.utils.ts
index 3134c20fc..8e0ae55fc 100644
--- a/apps/server/src/api-integration/integration.utils.ts
+++ b/apps/server/src/api-integration/integration.utils.ts
@@ -23,14 +23,13 @@ const whitelistedPayload = {
 
 export function parseProperty(property: string, value: unknown) {
   if (property.startsWith('custom:')) {
-    const customKey = property.split(':')[1];
+    const customKey = property.split(':')[1].toLocaleLowerCase(); // all custom fields keys are lowercase
     if (!(customKey in DataProvider.getCustomFields())) {
       throw new Error(`Custom field ${customKey} not found`);
     }
     const parserFn = whitelistedPayload.custom;
     return { custom: { [customKey]: parserFn(value) } };
   }
-
   if (!isKeyOfType(property, whitelistedPayload)) {
     throw new Error(`Property ${property} not permitted`);
   }