diff --git a/ConfigSpace/forbidden.py b/ConfigSpace/forbidden.py
index ce7dadd2..0fab0aa2 100644
--- a/ConfigSpace/forbidden.py
+++ b/ConfigSpace/forbidden.py
@@ -32,12 +32,13 @@
 import io
 from functools import reduce
 
-from ConfigSpace.hyperparameters import Hyperparameter
 
+from ConfigSpace.hyperparameters import Hyperparameter
+from typing import List, Dict, Any, Union
 
 class AbstractForbiddenComponent(object):
     __metaclass__ = ABCMeta
-
+    hyperparameter = None  # type: Hyperparameter
     @abstractmethod
     def __init__(self):
         pass
@@ -47,19 +48,19 @@ def __repr__(self):
         pass
 
     # http://stackoverflow.com/a/25176504/4636294
-    def __eq__(self, other):
+    def __eq__(self, other: Any) -> bool:
         """Override the default Equals behavior"""
         if isinstance(other, self.__class__):
             return self.__dict__ == other.__dict__
         return NotImplemented
 
-    def __ne__(self, other):
+    def __ne__(self, other: Any) -> bool:
         """Define a non-equality test"""
         if isinstance(other, self.__class__):
             return not self.__eq__(other)
         return NotImplemented
 
-    def __hash__(self):
+    def __hash__(self) -> int:
         """Override the default hash behavior (that returns the id or the object)"""
         return hash(tuple(sorted(self.__dict__.items())))
 
@@ -68,17 +69,17 @@ def get_descendant_literal_clauses(self):
         pass
 
     @abstractmethod
-    def is_forbidden(self, instantiated_hyperparameters):
+    def is_forbidden(self, instantiated_hyperparameters, strict):
         pass
 
 
 class AbstractForbiddenClause(AbstractForbiddenComponent):
-    def get_descendant_literal_clauses(self):
+    def get_descendant_literal_clauses(self) -> List[AbstractForbiddenComponent]:
         return [self]
 
 
 class SingleValueForbiddenClause(AbstractForbiddenClause):
-    def __init__(self, hyperparameter, value):
+    def __init__(self, hyperparameter: Hyperparameter, value: Any) -> None:
         super(SingleValueForbiddenClause, self).__init__()
         if not isinstance(hyperparameter, Hyperparameter):
             raise TypeError("'%s' is not of type %s." %
@@ -90,7 +91,7 @@ def __init__(self, hyperparameter, value):
                              "'%s'" % (hyperparameter, str(value)))
         self.value = value
 
-    def is_forbidden(self, instantiated_hyperparameters, strict=True):
+    def is_forbidden(self, instantiated_hyperparameters: Dict[str, Union[None, str, float, int]], strict: bool=True) -> bool:
         value = instantiated_hyperparameters.get(self.hyperparameter.name)
 
         if value is None:
@@ -110,7 +111,7 @@ def _is_forbidden(self, target_instantiated_hyperparameter):
 
 
 class MultipleValueForbiddenClause(AbstractForbiddenClause):
-    def __init__(self, hyperparameter, values):
+    def __init__(self, hyperparameter: Hyperparameter, values: Any) -> None:
         super(MultipleValueForbiddenClause, self).__init__()
         if not isinstance(hyperparameter, Hyperparameter):
             raise TypeError("Argument 'hyperparameter' is not of type %s." %
@@ -123,7 +124,7 @@ def __init__(self, hyperparameter, values):
                                  "'%s'" % (hyperparameter, str(value)))
         self.values = values
 
-    def is_forbidden(self, instantiated_hyperparameters, strict=True):
+    def is_forbidden(self, instantiated_hyperparameters: Dict[str, Union[None, str, float, int]], strict: bool=True) -> bool:
         value = instantiated_hyperparameters.get(self.hyperparameter.name)
 
         if value is None:
@@ -143,31 +144,31 @@ def _is_forbidden(self, target_instantiated_hyperparameter):
 
 
 class ForbiddenEqualsClause(SingleValueForbiddenClause):
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "Forbidden: %s == %s" % (self.hyperparameter.name,
                                         repr(self.value))
 
-    def _is_forbidden(self, value):
+    def _is_forbidden(self, value: Any) -> bool:
         return value == self.value
 
 
 class ForbiddenInClause(MultipleValueForbiddenClause):
-    def __init__(self, hyperparameter, values):
+    def __init__(self, hyperparameter: Dict[str, Union[None, str, float, int]], values: Any) -> None:
         super(ForbiddenInClause, self).__init__(hyperparameter, values)
         self.values = set(self.values)
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "Forbidden: %s in %s" % (
             self.hyperparameter.name,
             "{" + ", ".join((repr(value)
                              for value in sorted(self.values))) + "}")
 
-    def _is_forbidden(self, value):
+    def _is_forbidden(self, value: Any) -> bool:
         return value in self.values
 
 
 class AbstractForbiddenConjunction(AbstractForbiddenComponent):
-    def __init__(self, *args):
+    def __init__(self, *args: AbstractForbiddenComponent) -> None:
         super(AbstractForbiddenConjunction, self).__init__()
         # Test the classes
         for idx, component in enumerate(args):
@@ -183,7 +184,8 @@ def __init__(self, *args):
     def __repr__(self):
         pass
 
-    def get_descendant_literal_clauses(self):
+    # todo:recheck is return type should be AbstractForbiddenComponent or AbstractForbiddenConjunction or Hyperparameter
+    def get_descendant_literal_clauses(self) -> List[AbstractForbiddenComponent]:
         children = []
         for component in self.components:
             if isinstance(component, AbstractForbiddenConjunction):
@@ -192,7 +194,7 @@ def get_descendant_literal_clauses(self):
                 children.append(component)
         return children
 
-    def is_forbidden(self, instantiated_hyperparameters, strict=True):
+    def is_forbidden(self, instantiated_hyperparameters: Dict[str, Union[None, str, float, int]], strict: bool=True) -> bool:
         ihp_names = list(instantiated_hyperparameters.keys())
 
         dlcs = self.get_descendant_literal_clauses()
@@ -222,7 +224,7 @@ def _is_forbidden(self, evaluations):
 
 
 class ForbiddenAndConjunction(AbstractForbiddenConjunction):
-    def __repr__(self):
+    def __repr__(self) -> str:
         retval = io.StringIO()
         retval.write("(")
         for idx, component in enumerate(self.components):
@@ -232,5 +234,5 @@ def __repr__(self):
         retval.write(")")
         return retval.getvalue()
 
-    def _is_forbidden(self, evaluations):
+    def _is_forbidden(self, evaluations: List[bool]) -> bool:
         return reduce(operator.and_, evaluations)