diff --git a/jsgc.c b/jsgc.c
index 3b65bdf..b6dd406 100644
--- a/jsgc.c
+++ b/jsgc.c
@@ -46,6 +46,8 @@ static void jsG_freeobject(js_State *J, js_Object *obj)
 		jsG_freeiterator(J, obj->u.iter.head);
 	if (obj->type == JS_CUSERDATA && obj->u.user.finalize)
 		obj->u.user.finalize(J, obj->u.user.data);
+	if (obj->type == JS_CCFUNCTION && obj->u.c.finalize)
+		obj->u.c.finalize(J, obj->u.c.data);
 	js_free(J, obj);
 }
 
diff --git a/jsrun.c b/jsrun.c
index 990d355..e6d6a96 100644
--- a/jsrun.c
+++ b/jsrun.c
@@ -176,10 +176,20 @@ void js_pushglobal(js_State *J)
 void js_currentfunction(js_State *J)
 {
 	CHECKSTACK(1);
-	STACK[TOP] = STACK[BOT-1];
+	if (BOT > 0)
+		STACK[TOP] = STACK[BOT-1];
+	else
+		STACK[TOP].type = JS_TUNDEFINED;
 	++TOP;
 }
 
+void *js_currentfunctiondata(js_State *J)
+{
+	if (BOT > 0)
+		return STACK[BOT-1].u.object->u.c.data;
+	return NULL;
+}
+
 /* Read values from stack */
 
 static js_Value *stackidx(js_State *J, int idx)
diff --git a/jsvalue.c b/jsvalue.c
index a465a0b..b97a580 100644
--- a/jsvalue.c
+++ b/jsvalue.c
@@ -463,13 +463,15 @@ void js_newscript(js_State *J, js_Function *fun, js_Environment *scope)
 	js_pushobject(J, obj);
 }
 
-void js_newcfunction(js_State *J, js_CFunction cfun, const char *name, int length)
+void js_newcfunctionx(js_State *J, js_CFunction cfun, const char *name, int length, void *data, js_Finalize finalize)
 {
 	js_Object *obj = jsV_newobject(J, JS_CCFUNCTION, J->Function_prototype);
 	obj->u.c.name = name;
 	obj->u.c.function = cfun;
 	obj->u.c.constructor = NULL;
 	obj->u.c.length = length;
+	obj->u.c.data = data;
+	obj->u.c.finalize = finalize;
 	js_pushobject(J, obj);
 	{
 		js_pushnumber(J, length);
@@ -483,6 +485,11 @@ void js_newcfunction(js_State *J, js_CFunction cfun, const char *name, int lengt
 	}
 }
 
+void js_newcfunction(js_State *J, js_CFunction cfun, const char *name, int length)
+{
+	js_newcfunctionx(J, cfun, name, length, NULL, NULL);
+}
+
 /* prototype -- constructor */
 void js_newcconstructor(js_State *J, js_CFunction cfun, js_CFunction ccon, const char *name, int length)
 {
diff --git a/jsvalue.h b/jsvalue.h
index dbb7b4b..880efe4 100644
--- a/jsvalue.h
+++ b/jsvalue.h
@@ -103,6 +103,8 @@ struct js_Object
 			js_CFunction function;
 			js_CFunction constructor;
 			int length;
+			void *data;
+			js_Finalize finalize;
 		} c;
 		js_Regexp r;
 		struct {
diff --git a/mujs.h b/mujs.h
index 3cc6a56..421e81a 100644
--- a/mujs.h
+++ b/mujs.h
@@ -149,6 +149,7 @@ void js_setindex(js_State *J, int idx, int i);
 void js_delindex(js_State *J, int idx, int i);
 
 void js_currentfunction(js_State *J);
+void *js_currentfunctiondata(js_State *J);
 void js_pushglobal(js_State *J);
 void js_pushundefined(js_State *J);
 void js_pushnull(js_State *J);
@@ -165,6 +166,7 @@ void js_newboolean(js_State *J, int v);
 void js_newnumber(js_State *J, double v);
 void js_newstring(js_State *J, const char *v);
 void js_newcfunction(js_State *J, js_CFunction fun, const char *name, int length);
+void js_newcfunctionx(js_State *J, js_CFunction fun, const char *name, int length, void *data, js_Finalize finalize);
 void js_newcconstructor(js_State *J, js_CFunction fun, js_CFunction con, const char *name, int length);
 void js_newuserdata(js_State *J, const char *tag, void *data, js_Finalize finalize);
 void js_newuserdatax(js_State *J, const char *tag, void *data, js_HasProperty has, js_Put put, js_Delete del, js_Finalize finalize);