diff --git a/Examples/test-suite/python/struct_value_runme.py b/Examples/test-suite/python/struct_value_runme.py
index 727996f53..a20e83439 100644
--- a/Examples/test-suite/python/struct_value_runme.py
+++ b/Examples/test-suite/python/struct_value_runme.py
@@ -7,3 +7,24 @@ if b.a.x != 3: raise RuntimeError
 
 b.b.x = 3
 if b.b.x != 3: raise RuntimeError
+
+
+# Test dynamically added attributes - Github pull request #320
+b.added = 123
+
+if b.added != 123:
+  raise RuntimeError("Wrong attribute value")
+
+if not b.__dict__.has_key("added"):
+  raise RuntimeError("Missing added attribute in __dict__")
+
+class PyBar(struct_value.Bar):
+  def __init__(self):
+    self.extra = "hi"
+    struct_value.Bar.__init__(self)
+
+pybar = PyBar()
+if not pybar.__dict__.has_key("extra"):
+  raise RuntimeError("Missing extra attribute in __dict__")
+if pybar.extra != "hi":
+  raise RuntimeError("Incorrect attribute value for extra")
diff --git a/Lib/python/builtin.swg b/Lib/python/builtin.swg
index 28c557a21..1d892375c 100644
--- a/Lib/python/builtin.swg
+++ b/Lib/python/builtin.swg
@@ -9,6 +9,7 @@ SWIGINTERN void					\
 wrapper##_closure(PyObject *a) {		\
     SwigPyObject *sobj;				\
     sobj = (SwigPyObject *)a;			\
+    Py_XDECREF(sobj->dict);	                \
     if (sobj->own) {				\
 	PyObject *o = wrapper(a, NULL);		\
 	Py_XDECREF(o);				\
diff --git a/Lib/python/pyrun.swg b/Lib/python/pyrun.swg
index a713486d1..7ef8d5e39 100644
--- a/Lib/python/pyrun.swg
+++ b/Lib/python/pyrun.swg
@@ -381,6 +381,23 @@ typedef struct {
 #endif
 } SwigPyObject;
 
+
+#ifdef SWIGPYTHON_BUILTIN
+
+SWIGRUNTIME PyObject *
+SwigPyObject_get___dict__(PyObject *v, PyObject *SWIGUNUSEDPARM(args))
+{
+  SwigPyObject *sobj = (SwigPyObject *)v;
+
+  if (!sobj->dict)
+    sobj->dict = PyDict_New();
+
+  Py_INCREF(sobj->dict);
+  return sobj->dict;
+}
+
+#endif
+
 SWIGRUNTIME PyObject *
 SwigPyObject_long(SwigPyObject *v)
 {
@@ -1420,18 +1437,21 @@ SWIG_Python_NewPointerObj(PyObject *self, void *ptr, swig_type_info *type, int f
 	  newobj = (SwigPyObject *) newobj->next;
         newobj->next = next_self;
         newobj = (SwigPyObject *)next_self;
+#ifdef SWIGPYTHON_BUILTIN
+        newobj->dict = 0;
+#endif
       }
     } else {
       newobj = PyObject_New(SwigPyObject, clientdata->pytype);
+#ifdef SWIGPYTHON_BUILTIN
+      newobj->dict = 0;
+#endif
     }
     if (newobj) {
       newobj->ptr = ptr;
       newobj->ty = type;
       newobj->own = own;
       newobj->next = 0;
-#ifdef SWIGPYTHON_BUILTIN
-      newobj->dict = 0;
-#endif
       return (PyObject*) newobj;
     }
     return SWIG_Py_Void();
diff --git a/Source/Modules/python.cxx b/Source/Modules/python.cxx
index 0e4a40229..bc31c4264 100644
--- a/Source/Modules/python.cxx
+++ b/Source/Modules/python.cxx
@@ -3058,6 +3058,17 @@ public:
     }
 
     /* If this is a builtin type, create a PyGetSetDef entry for this member variable. */
+    if (builtin) {
+      const char *memname = "__dict__";
+      Hash *h = Getattr(builtin_getset, memname);
+      if (!h) {
+        h = NewHash();
+        Setattr(builtin_getset, memname, h);
+        Delete(h);
+      }
+      Setattr(h, "getter", "SwigPyObject_get___dict__");
+    }
+
     if (builtin_getter) {
       String *memname = Getattr(n, "membervariableHandler:sym:name");
       if (!memname)