diff --git a/src/upload/upload.service.ts b/src/upload/upload.service.ts
index fb25f7c..51b79ea 100644
--- a/src/upload/upload.service.ts
+++ b/src/upload/upload.service.ts
@@ -33,6 +33,10 @@ export class UploadService {
         secretAccessKey:
           this.configService.get<string>('AWS_SECRET_ACCESS_KEY') || '',
       },
+      // Disable AWS SDK v3 default checksum behavior — DO Spaces / Contabo / MinIO
+      // don't support the new x-amz-checksum-* headers and reject CORS preflights.
+      requestChecksumCalculation: 'WHEN_REQUIRED',
+      responseChecksumValidation: 'WHEN_REQUIRED',
     };
 
     // Add custom endpoint for S3-compatible services (Contabo, MinIO, DigitalOcean, etc.)