diff --git a/src/DIRAC/DataManagementSystem/Service/S3GatewayHandler.py b/src/DIRAC/DataManagementSystem/Service/S3GatewayHandler.py
index fde22548d77..5f80b9d1355 100644
--- a/src/DIRAC/DataManagementSystem/Service/S3GatewayHandler.py
+++ b/src/DIRAC/DataManagementSystem/Service/S3GatewayHandler.py
@@ -151,9 +151,9 @@ def export_createPresignedUrl(self, storageName, s3_method, urls, expiration):
                     failed[url] = "Permission denied"
                     continue
 
-                res = returnSingleResult(
-                    s3Plugin.createPresignedUrl({url: urls.get("Fields")}, s3_method, expiration=expiration)
-                )
+                # For put_object, urls maps each url to the fields (metadata) of the file
+                fields = urls[url] if s3_method == "put_object" else None
+                res = returnSingleResult(s3Plugin.createPresignedUrl({url: fields}, s3_method, expiration=expiration))
 
                 log.debug(f"Presigned URL for {url}: {res}")
                 if res["OK"]:
diff --git a/src/DIRAC/Resources/Storage/S3Storage.py b/src/DIRAC/Resources/Storage/S3Storage.py
index 5826b31c5ad..b904c4f18cc 100644
--- a/src/DIRAC/Resources/Storage/S3Storage.py
+++ b/src/DIRAC/Resources/Storage/S3Storage.py
@@ -268,7 +268,8 @@ def _presigned_exists(self, urls):
         # and perform it with requests
         for url, presignedURL in presignedURLs.items():
             try:
-                response = requests.get(presignedURL)
+                # The URL is signed for head_object so it must be used with HEAD
+                response = requests.head(presignedURL)
                 if response.status_code == 200:
                     successful[url] = True
                 elif response.status_code == 404:  # not found
@@ -768,8 +769,10 @@ def createPresignedUrl(self, urls, s3_method, expiration=3600):
                     fields = keys.get(key)
                     if not isinstance(fields, dict):
                         fields = None
+                    # boto does not add the fields to the policy, without which S3 rejects them
+                    conditions = [{k: v} for k, v in fields.items()] if fields else None
                     response = self.s3_client.generate_presigned_post(
-                        self.bucketName, key, Fields=fields, ExpiresIn=expiration
+                        self.bucketName, key, Fields=fields, Conditions=conditions, ExpiresIn=expiration
                     )
 
                 successful[key] = response