@@ -34,16 +34,16 @@
 
 	return 0;
 }
 
 @implementation OFThread
-+ threadWithObject: (id)obj
++ threadWithObject: (OFObject <OFCopying>*)obj
 {
 	return [[[self alloc] initWithObject: obj] autorelease];
 }
 
-+ setObject: (id)obj
++ setObject: (OFObject*)obj
   forTLSKey: (OFTLSKey*)key
 {
 	id old = of_tlskey_get(key->key);
 
 	if (!of_tlskey_set(key->key, [obj retain]))
@@ -64,11 +64,11 @@
 {
 	@throw [OFNotImplementedException newWithClass: isa
 					      selector: _cmd];
 }
 
-- initWithObject: (id)obj
+- initWithObject: (OFObject <OFCopying>*)obj
 {
 	self = [super init];
 	object = [obj copy];
 
 	if (!of_thread_new(&thread, call_main, self)) {