diff --git a/bob/bio/base/extractor/stacks.py b/bob/bio/base/extractor/stacks.py
index 8bc5aee5db9f755fc6520d5b68b764c9ae811e50..98cb83ce3ea4d18470a6b1ffca85900e4c99312f 100644
--- a/bob/bio/base/extractor/stacks.py
+++ b/bob/bio/base/extractor/stacks.py
@@ -8,7 +8,7 @@ class MultipleExtractor(Extractor):
   not meant to be used directly."""
 
   def get_attributes(self, processors):
-    requires_training = any((p.requires_training for p in processors))
+    requires_training = any(p.requires_training for p in processors)
     split_training_data_by_client = any(p.split_training_data_by_client for p
                                         in processors)
     min_extractor_file_size = min(p.min_extractor_file_size for p in
diff --git a/bob/bio/base/preprocessor/stacks.py b/bob/bio/base/preprocessor/stacks.py
index af96a736f02dc39b8deaaa25dd072b79e0428a8c..d782291514210a7518d2655b38e48370a01284f9 100644
--- a/bob/bio/base/preprocessor/stacks.py
+++ b/bob/bio/base/preprocessor/stacks.py
@@ -26,8 +26,8 @@ class ParallelPreprocessor(ParallelProcessor, Preprocessor):
   __doc__ = ParallelProcessor.__doc__
 
   def __init__(self, processors, **kwargs):
-    min_preprocessed_file_size = min((p.min_preprocessed_file_size for p in
-                                      processors))
+    min_preprocessed_file_size = min(p.min_preprocessed_file_size for p in
+                                     processors)
 
     ParallelProcessor.__init__(self, processors)
     Preprocessor.__init__(