diff --git a/RucioClient.py b/RucioClient.py
index 3f014a22a..517c15c79 100755
--- a/RucioClient.py
+++ b/RucioClient.py
@@ -75,6 +75,8 @@ def getFileCountBlock(self, block):
         """
         try:
             numFiles = self.get_metadata(self.scope, block)['length']
+            if numFiles is None:
+                raise Exception("block length in rucio is None")
         except Exception as e:
             print(str(e))
             return 0
@@ -91,6 +93,6 @@ def getFileCountPerBlock(self, dataset):
                 blocks.append((block, self.getFileCountBlock(block)))
         except Exception as e:
             print(str(e))
-            return 0
+            return []
         return blocks