diff --git a/mercadopago/webhook/validator.py b/mercadopago/webhook/validator.py
index 835b569..8edbcda 100644
--- a/mercadopago/webhook/validator.py
+++ b/mercadopago/webhook/validator.py
@@ -105,7 +105,7 @@ def validate(  # pylint: disable=too-many-arguments
                 the manifest before computing the HMAC.
             data_id: Value of the ``data.id`` query parameter. May be ``None``;
                 in that case the ``id:`` pair is omitted. When present, the
-                value is lowercased before being included in the manifest.
+                value is included in the manifest exactly as received.
             secret: Secret signature configured for the application in Tus
                 Integraciones.
             tolerance_seconds: Optional maximum allowed drift in seconds
@@ -216,7 +216,7 @@ def _build_manifest(data_id, request_id, ts):
     """Builds the HMAC manifest, omitting empty pairs per the documented rule."""
     parts = []
     if data_id:
-        parts.append(f"id:{data_id.lower()}")
+        parts.append(f"id:{data_id}")
     if request_id:
         parts.append(f"request-id:{request_id}")
     parts.append(f"ts:{ts}")
diff --git a/tests/test_webhook_signature_validator.py b/tests/test_webhook_signature_validator.py
index ba8b87a..8a3b5d1 100644
--- a/tests/test_webhook_signature_validator.py
+++ b/tests/test_webhook_signature_validator.py
@@ -28,7 +28,7 @@
 def compute_hash(data_id, request_id, ts, secret):
     parts = []
     if data_id:
-        parts.append(f"id:{data_id.lower()}")
+        parts.append(f"id:{data_id}")
     if request_id:
         parts.append(f"request-id:{request_id}")
     parts.append(f"ts:{ts}")
@@ -52,8 +52,10 @@ def test_happy_path_lowercase(self):
         WebhookSignatureValidator.validate(VALID_HEADER, REQUEST_ID, DATA_ID_LOWER, SECRET)
 
     # --- case 2 ---
-    def test_uppercase_dataid_is_lowercased(self):
-        WebhookSignatureValidator.validate(VALID_HEADER, REQUEST_ID, DATA_ID_RAW, SECRET)
+    def test_uppercase_dataid_is_preserved(self):
+        upper_hash = compute_hash(DATA_ID_RAW, REQUEST_ID, TS, SECRET)
+        upper_header = build_header(upper_hash)
+        WebhookSignatureValidator.validate(upper_header, REQUEST_ID, DATA_ID_RAW, SECRET)
 
     # --- case 3 ---
     def test_malformed_header_raises_malformed(self):