diff --git a/jedi/api/__init__.py b/jedi/api/__init__.py
index 557c6a1b..c0142f78 100644
--- a/jedi/api/__init__.py
+++ b/jedi/api/__init__.py
@@ -286,7 +286,7 @@ class Script(object):
                             if new_name.start_pos is None:
                                 found_builtin = True
 
-                    if found_builtin and not isinstance(name, imports.SubModuleName):
+                    if found_builtin:
                         yield name
                     else:
                         for new_name in new_names:
@@ -305,7 +305,7 @@ class Script(object):
                 return name.is_import()
         else:
             def check(name):
-                return isinstance(name, imports.SubModuleName)
+                return False
 
         names = filter_follow_imports(names, check)
         names = try_stub_to_actual_names(names, prefer_stub_to_compiled=True)
diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index 24868a61..b03c6728 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -64,15 +64,22 @@ class BaseDefinition(object):
         """
         self.is_keyword = isinstance(self._name, KeywordName)
 
-        # generate a path to the definition
-        self._module = name.get_root_context()
+    @memoize_method
+    def _get_module(self):
+        # This can take a while to complete, because in the worst case of
+        # imports (consider `import a` completions), we need to load all
+        # modules starting with a first.
+        return self._name.get_root_context()
+
+    @property
+    def module_path(self):
+        """Shows the file path of a module. e.g. ``/usr/lib/python2.7/os.py``"""
         try:
-            py__file__ = self._module.py__file__
+            py__file__ = self._get_module().py__file__
         except AttributeError:
-            self.module_path = None
+            return None
         else:
-            self.module_path = py__file__()
-            """Shows the file path of a module. e.g. ``/usr/lib/python2.7/os.py``"""
+            return py__file__()
 
     @property
     def name(self):
@@ -203,14 +210,14 @@ class BaseDefinition(object):
         >>> print(d.module_name)                       # doctest: +ELLIPSIS
         json
         """
-        return self._module.name.string_name
+        return self._get_module().name.string_name
 
     def in_builtin_module(self):
         """Whether this is a builtin module."""
-        if isinstance(self._module, StubModuleContext):
+        if isinstance(self._get_module(), StubModuleContext):
             return any(isinstance(context, compiled.CompiledObject)
-                       for context in self._module.non_stub_context_set)
-        return isinstance(self._module, compiled.CompiledObject)
+                       for context in self._get_module().non_stub_context_set)
+        return isinstance(self._get_module(), compiled.CompiledObject)
 
     @property
     def line(self):
diff --git a/jedi/evaluate/names.py b/jedi/evaluate/names.py
index 8fbae523..56a782af 100644
--- a/jedi/evaluate/names.py
+++ b/jedi/evaluate/names.py
@@ -4,6 +4,7 @@ from parso.tree import search_ancestor
 
 from jedi._compatibility import Parameter
 from jedi.evaluate.base_context import ContextSet
+from jedi.cache import memoize_method
 
 
 class AbstractNameDefinition(object):
@@ -139,25 +140,28 @@ class ImportName(AbstractNameDefinition):
     _level = 0
 
     def __init__(self, parent_context, string_name):
-        self.parent_context = parent_context
+        self._from_module_context = parent_context
         self.string_name = string_name
 
+    @property
+    def parent_context(self):
+        m = self._from_module_context
+        import_contexts = self.infer()
+        if not import_contexts:
+            return m
+        # It's almost always possible to find the import or to not find it. The
+        # importing returns only one context, pretty much always.
+        return next(iter(import_contexts))
+
+    @memoize_method
     def infer(self):
         from jedi.evaluate.imports import Importer
-        return Importer(
-            self.parent_context.evaluator,
-            [self.string_name],
-            self.parent_context,
-            level=self._level,
-        ).follow()
+        m = self._from_module_context
+        return Importer(m.evaluator, [self.string_name], m, level=self._level).follow()
 
     def goto(self):
         return [m.name for m in self.infer()]
 
-    def get_root_context(self):
-        # Not sure if this is correct.
-        return self.parent_context.get_root_context()
-
     @property
     def api_type(self):
         return 'module'