--- a/filesystem.c
+++ b/filesystem.c
@@ -113,7 +113,7 @@ static VALUE fs_stat(VALUE obj, VALUE di
 		INT2NUM(fs.f_favail),
 		INT2NUM(fs.f_flag),
 		INT2NUM(fs.f_namemax),
-		0 );
+		NULL );
 }
 
 void Init_filesystem()
@@ -124,7 +124,7 @@ void Init_filesystem()
 
 	sFSstat = rb_struct_define("FileSystemStat",
 		"path", "block_size", "blocks", "blocks_free", "blocks_avail", 
-		"files", "files_free", "files_avail", "flags", "maxnamelen", 0);
+		"files", "files_free", "files_avail", "flags", "maxnamelen", NULL);
 	rb_global_variable(&sFSstat);
 
 	sFSmount = rb_struct_define("FileSystemMount",
@@ -134,7 +134,7 @@ void Init_filesystem()
 #else
 		"dump_interval", "check_pass",
 #endif
-	       	0);
+	       	NULL);
 	rb_global_variable(&sFSmount);
 
 
