diff --git a/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/__tests__/cast-to-log-level-array.decorator.spec.ts b/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/__tests__/cast-to-log-level-array.decorator.spec.ts
index 4cd656dff4..25e9d53a57 100644
--- a/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/__tests__/cast-to-log-level-array.decorator.spec.ts
+++ b/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/__tests__/cast-to-log-level-array.decorator.spec.ts
@@ -50,17 +50,17 @@ describe('CastToLogLevelArray Decorator', () => {
     ]);
   });
 
-  it('should cast "toto" to undefined', () => {
-    const transformedClass = plainToClass(TestClass, { logLevels: 'toto' });
-
-    expect(transformedClass.logLevels).toBeUndefined();
+  it('should throw on invalid level "toto" with clear error message', () => {
+    expect(() => plainToClass(TestClass, { logLevels: 'toto' })).toThrow(
+      'Invalid log level(s): toto. Valid levels are: log, error, warn, debug, verbose',
+    );
   });
 
-  it('should cast "verbose,error,toto" to undefined', () => {
-    const transformedClass = plainToClass(TestClass, {
-      logLevels: 'verbose,error,toto',
-    });
-
-    expect(transformedClass.logLevels).toBeUndefined();
+  it('should throw on "verbose,error,toto" listing only invalid levels', () => {
+    expect(() =>
+      plainToClass(TestClass, { logLevels: 'verbose,error,toto' }),
+    ).toThrow(
+      'Invalid log level(s): toto. Valid levels are: log, error, warn, debug, verbose',
+    );
   });
 });
diff --git a/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/cast-to-log-level-array.decorator.ts b/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/cast-to-log-level-array.decorator.ts
index bf3b14906d..489db3b4cd 100644
--- a/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/cast-to-log-level-array.decorator.ts
+++ b/packages/twenty-server/src/engine/core-modules/twenty-config/decorators/cast-to-log-level-array.decorator.ts
@@ -1,5 +1,7 @@
 import { Transform } from 'class-transformer';
 
+const VALID_LOG_LEVELS = ['log', 'error', 'warn', 'debug', 'verbose'];
+
 export const CastToLogLevelArray = () =>
   Transform(({ value }: { value: string }) => toLogLevelArray(value));
 
@@ -7,13 +9,17 @@ export const CastToLogLevelArray = () =>
 const toLogLevelArray = (value: any) => {
   if (typeof value === 'string') {
     const rawLogLevels = value.split(',').map((level) => level.trim());
-    const isInvalid = rawLogLevels.some(
-      (level) => !['log', 'error', 'warn', 'debug', 'verbose'].includes(level),
+    const invalidLevels = rawLogLevels.filter(
+      (level) => !VALID_LOG_LEVELS.includes(level),
     );
 
-    if (!isInvalid) {
-      return rawLogLevels;
+    if (invalidLevels.length > 0) {
+      throw new Error(
+        `Invalid log level(s): ${invalidLevels.join(', ')}. Valid levels are: ${VALID_LOG_LEVELS.join(', ')}`,
+      );
     }
+
+    return rawLogLevels;
   }
 
   return undefined;