diff --git a/naive-nlu/tree_nlu/knowledge_base.py b/naive-nlu/tree_nlu/knowledge_base.py
index 28ad221..f33b39f 100644
--- a/naive-nlu/tree_nlu/knowledge_base.py
+++ b/naive-nlu/tree_nlu/knowledge_base.py
@@ -70,11 +70,11 @@ class KnowledgeBase(object):
     def process(self, row):
         knowledge_before = copy.deepcopy(self.knowledge)
         with session().log("Process: {}".format(row)):
-            fit = self.layers.process(self, row)
-            if fit is None:
+            fit = list(self.layers.process(self, row))
+            if len(fit) == 0:
                 return None
 
-            tokens, inferred_tree = fit
+            tokens, inferred_tree = fit[0]
             result = knowledge_evaluation.integrate_information(self.knowledge,
                                                                 {
                                                                     "elements": tokens,
diff --git a/naive-nlu/tree_nlu/layers/parsing_layer.py b/naive-nlu/tree_nlu/layers/parsing_layer.py
index b631c75..2bfda2a 100644
--- a/naive-nlu/tree_nlu/layers/parsing_layer.py
+++ b/naive-nlu/tree_nlu/layers/parsing_layer.py
@@ -11,4 +11,6 @@ class ParsingLayer:
         assert False
 
     def process(self, knowledge_base, input):
-        yield from parsing.get_fit(knowledge_base, input)
\ No newline at end of file
+        fit = parsing.get_fit(knowledge_base, input)
+        if fit is not None:
+            yield fit
\ No newline at end of file