diff --git a/jedi/builtin.py b/jedi/builtin.py
index c0e76a8b..301bb10a 100644
--- a/jedi/builtin.py
+++ b/jedi/builtin.py
@@ -24,7 +24,7 @@ class CachedModule(object):
     cache = {}
 
     def __init__(self, path=None, name=None):
-        self.path = path
+        self.path = path and os.path.abspath(path)
         self.name = name
         self._parser = None
 
diff --git a/jedi/dynamic.py b/jedi/dynamic.py
index 11d4ad7f..e1b35984 100644
--- a/jedi/dynamic.py
+++ b/jedi/dynamic.py
@@ -41,20 +41,25 @@ def get_directory_modules_for_name(mods, name):
             if name in source:
                 return modules.Module(path, source).parser.module
 
+    # skip non python modules
+    mods = set(m for m in mods if m.path.endswith('.py'))
     mod_paths = set()
     for m in mods:
         mod_paths.add(m.path)
+        yield m
 
-    new = set()
+    paths = set(settings.additional_dynamic_modules)
     for p in mod_paths:
         d = os.path.dirname(p)
         for entry in os.listdir(d):
             if entry not in mod_paths:
                 if entry.endswith('.py'):
-                    c = check_python_file(d + os.path.sep + entry)
-                    if c is not None:
-                        new.add(c)
-    return set(mods) | new
+                    paths.add(d + os.path.sep + entry)
+
+    for p in paths:
+        c = check_python_file(p)
+        if c is not None and c not in mods:
+            yield c
 
 
 def search_param_memoize(func):
@@ -121,7 +126,6 @@ def search_params(param):
             for p in params:
                 if str(p) == param_name:
                     result += evaluate.follow_statement(p.parent())
-        #print listener.param_possibilities, param, result
 
         return result
 
@@ -143,9 +147,11 @@ def search_params(param):
     listener = ParamListener()
     func.listeners.add(listener)
 
-    result = get_params_for_module(current_module)
+    for mod in get_directory_modules_for_name([current_module], func_name):
+        result = get_params_for_module(mod)
+        if result:
+            break
 
-    # TODO check other modules
     # cleanup: remove the listener; important: should not stick.
     func.listeners.remove(listener)
 
@@ -380,9 +386,6 @@ def related_names(definitions, search_name, mods):
     mods |= set([d.get_parent_until() for d in definitions])
     names = []
     for m in get_directory_modules_for_name(mods, search_name):
-        if not m.path.endswith('.py'):
-            # don't search for names in builtin modules
-            continue
         try:
             stmts = m.used_names[search_name]
         except KeyError:
diff --git a/jedi/settings.py b/jedi/settings.py
index 02a38fb3..30b469db 100644
--- a/jedi/settings.py
+++ b/jedi/settings.py
@@ -28,6 +28,10 @@ dynamic_array_additions = True
 # the params of a function.
 dynamic_params = True
 
+# Additional modules in which Jedi checks if statements are to be found. This
+# is practical for IDE's, that want to administrate their modules themselves.
+additional_dynamic_modules = []
+
 # ----------------
 # recursions
 # ----------------
diff --git a/test/regression.py b/test/regression.py
index 9489662d..c144bbe7 100755
--- a/test/regression.py
+++ b/test/regression.py
@@ -18,7 +18,9 @@ class TestRegression(unittest.TestCase):
         script = api.Script(src, pos[0], pos[1], '')
         return script.get_definition()
 
-    def complete(self, src, pos):
+    def complete(self, src, pos=None):
+        if pos is None:
+            pos = 1, len(src)
         script = api.Script(src, pos[0], pos[1], '')
         return script.complete()
 
@@ -152,5 +154,19 @@ class TestRegression(unittest.TestCase):
 
         assert check(self.get_in_function_call(s7), 'center', 0)
 
+    def test_add_dynamic_mods(self):
+        api.settings.additional_dynamic_modules = ['dynamic.py']
+        # Fictional module that defines a function.
+        src1 = "def ret(a): return a"
+        # Other fictional modules in another place in the fs.
+        src2 = 'from .. import setup; setup.ret(1)'
+        # .parser to load the module
+        api.modules.Module(os.path.abspath('dynamic.py'), src2).parser
+        script = api.Script(src1, 1, len(src1), '../setup.py')
+        result = script.get_definition()
+        assert len(result) == 1
+        assert result[0].description == 'class int'
+
+
 if __name__ == '__main__':
     unittest.main()