diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index a1d42bd0..e5926ca8 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -322,7 +322,7 @@ class BaseDefinition(object):
         elif self._definition.isinstance(tree.Import):
             return imports.ImportWrapper(self._evaluator, self._name).follow()
         else:
-            return [self._definition]
+            return set([self._definition])
 
     @property
     @memoize_default()
@@ -331,7 +331,7 @@ class BaseDefinition(object):
         Raises an ``AttributeError``if the definition is not callable.
         Otherwise returns a list of `Definition` that represents the params.
         """
-        followed = self._follow_statements_imports()
+        followed = list(self._follow_statements_imports())
         if not followed or not hasattr(followed[0], 'py__call__'):
             raise AttributeError()
         followed = followed[0]  # only check the first one.
@@ -449,7 +449,7 @@ class Completion(BaseDefinition):
                 followed = self._follow_statements_imports()
                 if followed:
                     # TODO: Use all of the followed objects as input to Documentation.
-                    definition = followed[0]
+                    definition = list(followed)[0]
 
         if raw:
             return _Help(definition).raw()
diff --git a/jedi/evaluate/compiled/__init__.py b/jedi/evaluate/compiled/__init__.py
index d1da59d0..a28fed7f 100644
--- a/jedi/evaluate/compiled/__init__.py
+++ b/jedi/evaluate/compiled/__init__.py
@@ -194,7 +194,7 @@ class CompiledObject(Base):
         if not result:
             try:
                 for obj in self.obj:
-                    result.append(CompiledObject(obj))
+                    result.add(CompiledObject(obj))
             except TypeError:
                 pass  # self.obj maynot have an __iter__ method.
         return result
diff --git a/test/test_evaluate/test_compiled.py b/test/test_evaluate/test_compiled.py
index 2a6b28dc..c0977a48 100644
--- a/test/test_evaluate/test_compiled.py
+++ b/test/test_evaluate/test_compiled.py
@@ -12,7 +12,7 @@ def test_simple():
     obj = compiled.CompiledObject('_str_', bltn)
     upper = e.find_types(obj, 'upper')
     assert len(upper) == 1
-    objs = list(e.execute(upper[0]))
+    objs = list(e.execute(list(upper)[0]))
     assert len(objs) == 1
     assert isinstance(objs[0], representation.Instance)