diff --git a/jedi/cache.py b/jedi/cache.py
index 8dc82544..5f618375 100644
--- a/jedi/cache.py
+++ b/jedi/cache.py
@@ -91,6 +91,18 @@ def memoize_method(method):
     return wrapper
 
 
+def memoize_function(obj):
+    """ A normal memoize function for memoizing free functions. """
+    cache = obj.cache = {}
+
+    def memoizer(*args, **kwargs):
+        key = str(args) + str(kwargs)
+        if key not in cache:
+            cache[key] = obj(*args, **kwargs)
+        return cache[key]
+    return memoizer
+
+
 def cache_star_import(func):
     @time_cache("star_import_cache_validity")
     def wrapper(self):
diff --git a/jedi/evaluate/compiled/fake.py b/jedi/evaluate/compiled/fake.py
index 56eb2e28..9a422c11 100644
--- a/jedi/evaluate/compiled/fake.py
+++ b/jedi/evaluate/compiled/fake.py
@@ -9,6 +9,7 @@ import inspect
 import types
 
 from jedi._compatibility import is_py3, builtins, unicode, is_py34
+from jedi.cache import memoize_function
 from jedi.parser import ParserWithRecovery, load_grammar
 from jedi.parser import tree as pt
 from jedi.evaluate.helpers import FakeName
@@ -142,6 +143,7 @@ def _faked(module, obj, name):
             return search_scope(cls, name)
 
 
+@memoize_function
 def get_faked(module, obj, name=None):
     obj = type(obj) if is_class_instance(obj) else obj
     result = _faked(module, obj, name)
diff --git a/test/test_regression.py b/test/test_regression.py
index 48909798..abb10727 100644
--- a/test/test_regression.py
+++ b/test/test_regression.py
@@ -157,6 +157,29 @@ class TestRegression(TestCase):
             "abc()."
         assert Script(s).completions()
 
+    def test_fake_subnodes(self):
+        """
+        Test the number of subnodes of a fake object.
+
+        There was a bug where the number of child nodes would grow on every
+        call to :func:``jedi.evaluate.compiled.fake.get_faked``.
+
+        See Github PR#649 and isseu #591.
+        """
+        def get_str_completion(values):
+            for c in values:
+                if c.name == 'str':
+                    return c
+        limit = None
+        for i in range(2):
+            completions = Script('').completions()
+            c = get_str_completion(completions)
+            n = len(c._definition.subscopes[0].children[-1].children)
+            if i == 0:
+                limit = n
+            else:
+                assert n == limit
+
     def test_source_to_unicode_unicode_text(self):
         source = (
             b"# vim: fileencoding=utf-8\n"