diff -up php-5.2.17/Zend/zend_compile.c.bug-43200 php-5.2.17/Zend/zend_compile.c
--- php-5.2.17/Zend/zend_compile.c.bug-43200	2012-01-12 11:26:42.000000000 +0700
+++ php-5.2.17/Zend/zend_compile.c	2012-01-12 11:26:51.000000000 +0700
@@ -2080,7 +2080,8 @@ static zend_bool do_inherit_method_check
 		return 1; /* method doesn't exist in child, copy from parent */
 	}
 
-	if (parent->common.fn_flags & ZEND_ACC_ABSTRACT
+	if ((parent->common.scope->ce_flags & ZEND_ACC_INTERFACE) == 0
+		&& parent->common.fn_flags & ZEND_ACC_ABSTRACT
 		&& parent->common.scope != (child->common.prototype ? child->common.prototype->common.scope : child->common.scope)
 		&& child->common.fn_flags & (ZEND_ACC_ABSTRACT|ZEND_ACC_IMPLEMENTED_ABSTRACT)) {
 		zend_error(E_COMPILE_ERROR, "Can't inherit abstract function %s::%s() (previously declared abstract in %s)",