diff --git a/bob/bio/base/test/dummy/preprocessor.py b/bob/bio/base/test/dummy/preprocessor.py
index 7ccfcdcb7bd60750203bcf883b4d38ed1b973cb4..89376c31d59dd215b321153a6c56dbda75f32e0e 100644
--- a/bob/bio/base/test/dummy/preprocessor.py
+++ b/bob/bio/base/test/dummy/preprocessor.py
@@ -1,15 +1,19 @@
 from bob.bio.base.preprocessor import Preprocessor
+import numpy
+numpy.random.seed(10)
 
 
 class DummyPreprocessor (Preprocessor):
-  def __init__(self, return_none=False, **kwargs):
+  def __init__(self, return_none=False, probability_of_none=1, **kwargs):
     Preprocessor.__init__(self)
     self.return_none = return_none
+    self.probability_of_none = probability_of_none
 
   def __call__(self, data, annotation):
     """Does nothing, simply converts the data type of the data, ignoring any annotation."""
     if self.return_none:
-      return None
+      return numpy.random.choice([None, data], p=[self.probability_of_none, 1-self.probability_of_none])
+      
     return data
 
 
diff --git a/bob/bio/base/tools/preprocessor.py b/bob/bio/base/tools/preprocessor.py
index 045d1e71937598702f6480d68311740ac4cc7857..1f7374cf98a3d9135035eabfb76fd140491094d2 100644
--- a/bob/bio/base/tools/preprocessor.py
+++ b/bob/bio/base/tools/preprocessor.py
@@ -68,6 +68,7 @@ def preprocess(preprocessor, groups = None, indices = None, allow_missing_files
     if not utils.check_file(preprocessed_data_file, force,
                             preprocessor.min_preprocessed_file_size):
       logger.debug("... Processing original data file '%s'", file_name)
+
       data = preprocessor.read_original_data(file_object, original_directory, original_extension)
       # create output directory before reading the data file (is sometimes required, when relative directories are specified, especially, including a .. somewhere)
       bob.io.base.create_directories_safe(os.path.dirname(preprocessed_data_file))
diff --git a/setup.py b/setup.py
index f1a05cce60c7e8b6f8df75976322c01fddfa91bb..ca69ef786d52d4959fa331a1a0b83a735202c9a0 100644
--- a/setup.py
+++ b/setup.py
@@ -124,7 +124,7 @@ setup(
       ],
       # declare database to bob
       'bob.db': [
-        'bio_filelist = bob.bio.base.database.filelist.driver:Interface',
+        'bio_filelist      = bob.bio.base.database.filelist.driver:Interface',
       ],
    },