diff --git a/jedi/api.py b/jedi/api.py
index 654d4bdb..385d032f 100644
--- a/jedi/api.py
+++ b/jedi/api.py
@@ -198,7 +198,7 @@ class Script(object):
     :param col: The column to complete in.
     :type col: int
     :param source_path: The path in the os, the current module is in.
-    :type source_path: string
+    :type source_path: string or None
     """
     def __init__(self, source, line, column, source_path):
         self.pos = line, column
diff --git a/jedi/builtin.py b/jedi/builtin.py
index 13cd7da1..b5d9b31b 100644
--- a/jedi/builtin.py
+++ b/jedi/builtin.py
@@ -50,7 +50,8 @@ class CachedModule(object):
         self._parser = parsing.PyFuzzyParser(source, self.path or self.name)
         p_time = None if not self.path else os.path.getmtime(self.path)
 
-        self.cache[self.path or self.name] = p_time, self._parser
+        if self.path or self.name:
+            self.cache[self.path or self.name] = p_time, self._parser
 
 
 class Parser(CachedModule):
diff --git a/jedi/imports.py b/jedi/imports.py
index b3391080..deb21ac9 100644
--- a/jedi/imports.py
+++ b/jedi/imports.py
@@ -37,7 +37,8 @@ class ImportPath(object):
         self.is_like_search = is_like_search
         self.direct_resolve = direct_resolve
         self.is_partial_import = bool(kill_count)
-        self.file_path = os.path.dirname(import_stmt.get_parent_until().path)
+        path = import_stmt.get_parent_until().path
+        self.file_path = os.path.dirname(path) if path is not None else None
 
         # rest is import_path resolution
         self.import_path = []
@@ -198,9 +199,13 @@ class ImportPath(object):
                 sys.path = temp
                 return i
 
-        sys_path_mod = self.sys_path_with_modifications()
+        if self.file_path:
+            sys_path_mod = self.sys_path_with_modifications()
+            sys_path_mod.insert(0, self.file_path)
+        else:
+            sys_path_mod = builtin.module_find_path
+
         current_namespace = None
-        sys_path_mod.insert(0, self.file_path)
         # now execute those paths
         rest = []
         for i, s in enumerate(self.import_path):
diff --git a/jedi/modules.py b/jedi/modules.py
index 77a192a3..887248b4 100644
--- a/jedi/modules.py
+++ b/jedi/modules.py
@@ -40,7 +40,7 @@ class ModuleWithCursor(Module):
     be there.
 
     :param source: The source code of the file.
-    :param path: The module path of the file.
+    :param path: The module path of the file or None.
     :param position: The position, the user is currently in. Only important \
     for the main file.
     """
@@ -62,7 +62,8 @@ class ModuleWithCursor(Module):
         # Also, the position is here important (which will not be used by
         # default), therefore fill the cache here.
         self._parser = parsing.PyFuzzyParser(source, path, position)
-        builtin.CachedModule.cache[self.path] = time.time(), self._parser
+        if self.path:
+            builtin.CachedModule.cache[self.path] = time.time(), self._parser
 
     def get_path_until_cursor(self):
         """ Get the path under the cursor. """
diff --git a/jedi/parsing.py b/jedi/parsing.py
index 64361653..0c1b9797 100644
--- a/jedi/parsing.py
+++ b/jedi/parsing.py
@@ -300,7 +300,7 @@ class Module(Scope):
         return self._name
 
     def is_builtin(self):
-        return not self.path.endswith('.py')
+        return not (self.path is None or self.path.endswith('.py'))
 
 
 class Class(Scope):
diff --git a/test/regression.py b/test/regression.py
index 3ba21b8d..8c22a02c 100755
--- a/test/regression.py
+++ b/test/regression.py
@@ -16,7 +16,7 @@ import api
 
 class TestRegression(unittest.TestCase):
     def get_def(self, src, pos):
-        script = api.Script(src, pos[0], pos[1], '')
+        script = api.Script(src, pos[0], pos[1], None)
         return script.get_definition()
 
     def complete(self, src, pos=None):