diff --git a/ckanext/odsh/lib/uploader.py b/ckanext/odsh/lib/uploader.py
index d2b24ba8d004e3e55cca526a813e124a17f5a1ce..ab89260a54cada77b3de43f81834e2ab600bd67f 100644
--- a/ckanext/odsh/lib/uploader.py
+++ b/ckanext/odsh/lib/uploader.py
@@ -29,6 +29,7 @@ def _raise_validation_error_if_virus_found(filename, upload_file):
 
 
 def calculate_hash(upload_file):
+    upload_file.seek(0)
     hash_md5 = hashlib.md5()
     for chunk in iter(lambda: upload_file.read(4096), b""):
             hash_md5.update(chunk)
@@ -41,6 +42,8 @@ def _raise_validation_error_if_hash_values_differ(upload_file, resource):
     if hash_from_resource:
         hash_from_calculation = calculate_hash(upload_file)
         if not hash_from_calculation == hash_from_resource:
+            log.debug('hash from calculation: {}'.format(hash_from_calculation))
+            log.debug('hash from resource: {}'.format(hash_from_resource))
             raise logic.ValidationError({'upload': ['Berechneter Hash und mitgelieferter Hash sind unterschiedlich']})