diff --git a/sqlalchemy_mixins/serialize.py b/sqlalchemy_mixins/serialize.py
index 402ccc0..c52c03f 100644
--- a/sqlalchemy_mixins/serialize.py
+++ b/sqlalchemy_mixins/serialize.py
@@ -8,7 +8,7 @@ class SerializeMixin(InspectionMixin):
 
     __abstract__ = True
 
-    def to_dict(self,nested = False, hybrid_attributes = False, exclude = None):
+    def to_dict(self, nested=False, hybrid_attributes=False, exclude=None):
         """Return dict object with model's data.
 
         :param nested: flag to return nested relationships' data if true
@@ -17,26 +17,25 @@ def to_dict(self,nested = False, hybrid_attributes = False, exclude = None):
         :type: bool
         :return: dict
         """
-        result = dict()
-
         if exclude is None:
-             view_cols = self.columns
-        else :
-             view_cols = filter(lambda e: e not in exclude, self.columns)
-
-        for key in view_cols :
-            result[key] = getattr(self, key)
+            view_cols = self.columns
+            relations = self.relations
+        else:
+            view_cols = filter(lambda e: e not in exclude, self.columns)
+            relations = filter(lambda r: r not in exclude, self.relations)
 
+        result = {key: getattr(self, key) for key in view_cols}
         if hybrid_attributes:
             for key in self.hybrid_properties:
                 result[key] = getattr(self, key)
 
         if nested:
-            for key in self.relations:
+            for key in relations:
                 obj = getattr(self, key)
 
                 if isinstance(obj, SerializeMixin):
-                    result[key] = obj.to_dict(hybrid_attributes=hybrid_attributes)
+                    result[key] = obj.to_dict(
+                        hybrid_attributes=hybrid_attributes)
                 elif isinstance(obj, Iterable):
                     result[key] = [
                         o.to_dict(hybrid_attributes=hybrid_attributes) for o in obj