diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index 5fd11d4a..164da43b 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -8,8 +8,8 @@ import warnings
 from jedi._compatibility import next, unicode
 from jedi import settings
 from jedi import common
-from jedi import cache
 from jedi.parser import representation as pr
+from jedi.evaluate.cache import memoize_default
 from jedi.evaluate import representation as er
 from jedi.evaluate import iterable
 from jedi.evaluate import imports
@@ -300,8 +300,25 @@ class BaseDefinition(object):
 
         return stripped.is_callable()
 
+    @memoize_default()
+    def _follow_statements_imports(self):
+        if self._definition.isinstance(pr.Statement):
+            defs = self._evaluator.eval_statement(self._definition)
+        elif self._definition.isinstance(pr.Import):
+            if self._definition.alias is None:
+                i = imports.ImportPath(self._evaluator, self._definition, True)
+                defs = imports.Importer(i.import_path + [unicode(self._name)],
+                                        i._importer.module).follow(self._evaluator)
+            else:
+                defs = imports.strip_imports(self._evaluator, [self._definition])
+        else:
+            return [self]
+
+        defs = [BaseDefinition(self._evaluator, d, d.start_pos) for d in defs]
+        return defs
+
     @property
-    @cache.underscore_memoization
+    @memoize_default()
     def params(self):
         """
         Raises an ``AttributeError``if the definition is not callable.
@@ -465,7 +482,7 @@ class Completion(BaseDefinition):
                 return followed[0].type
         return super(Completion, self).type
 
-    @cache.underscore_memoization
+    @memoize_default()
     def follow_definition(self):
         """
         Return the original definitions. I strongly recommend not using it for
@@ -488,7 +505,6 @@ class Completion(BaseDefinition):
             return [self]
 
         defs = [BaseDefinition(self._evaluator, d, d.start_pos) for d in defs]
-        cache.clear_caches()
         return defs
 
 
@@ -607,7 +623,7 @@ class Definition(BaseDefinition):
         position = '' if self.in_builtin_module else '@%s' % (self.line)
         return "%s:%s%s" % (self.module_name, self.description, position)
 
-    @cache.underscore_memoization
+    @memoize_default()
     def defined_names(self):
         """
         List sub-definitions (e.g., methods in class).
diff --git a/jedi/evaluate/cache.py b/jedi/evaluate/cache.py
index d686f894..bf7a5342 100644
--- a/jedi/evaluate/cache.py
+++ b/jedi/evaluate/cache.py
@@ -5,7 +5,7 @@
 """
 
 
-def memoize_default(default, evaluator_is_first_arg=False, second_arg_is_evaluator=False):
+def memoize_default(default=None, evaluator_is_first_arg=False, second_arg_is_evaluator=False):
     """ This is a typical memoization decorator, BUT there is one difference:
     To prevent recursion it sets defaults.
 
diff --git a/jedi/evaluate/representation.py b/jedi/evaluate/representation.py
index 5cefcad4..6911a0e9 100644
--- a/jedi/evaluate/representation.py
+++ b/jedi/evaluate/representation.py
@@ -63,7 +63,7 @@ class Instance(use_metaclass(CachedMetaClass, Executable)):
         # (No var_args) used.
         self.is_generated = False
 
-    @memoize_default(None)
+    @memoize_default()
     def _get_method_execution(self, func):
         func = InstanceElement(self._evaluator, self, func, True)
         return FunctionExecution(self._evaluator, func, self.var_args)
@@ -203,7 +203,7 @@ class InstanceElement(use_metaclass(CachedMetaClass, pr.Base)):
         self.is_class_var = is_class_var
 
     @common.safe_property
-    @memoize_default(None)
+    @memoize_default()
     def parent(self):
         par = self.var.parent
         if isinstance(par, Class) and par == self.instance.base \
@@ -336,7 +336,7 @@ class Function(use_metaclass(CachedMetaClass, pr.IsScope)):
         self.base_func = func
         self.is_decorated = is_decorated
 
-    @memoize_default(None)
+    @memoize_default()
     def _decorated_func(self):
         """
         Returns the function, that is to be executed in the end.
@@ -476,7 +476,7 @@ class FunctionExecution(Executable):
             raise AttributeError('Tried to access %s: %s. Why?' % (name, self))
         return getattr(self.base, name)
 
-    @memoize_default(None)
+    @memoize_default()
     def _scope_copy(self, scope):
         """ Copies a scope (e.g. if) in an execution """
         # TODO method uses different scopes than the subscopes property.
diff --git a/test/test_api/test_api_classes.py b/test/test_api/test_api_classes.py
index c334be93..ecb89aa0 100644
--- a/test/test_api/test_api_classes.py
+++ b/test/test_api/test_api_classes.py
@@ -126,16 +126,16 @@ def test_completion_documentation():
 
 
 def test_signature_params():
+    def check(defs):
+        params = defs[0].params
+        assert len(params) == 1
+        assert params[0].name == 'bar'
+
     s = dedent('''
     def foo(bar):
         pass
     foo''')
 
-    defs = Script(s).goto_definitions()
-    params = defs[0].params
-    assert len(params) == 1
-    assert params[0].name == 'bar'
+    check(Script(s).goto_definitions())
 
-    defs = Script(s).goto_assignments()
-    with pytest.raises(AttributeError):
-        params = defs[0].params
+    check(Script(s).goto_assignments())