diff --git a/src/vapi/mpv.vapi b/src/vapi/mpv.vapi
index b599979..f3d8ade 100644
--- a/src/vapi/mpv.vapi
+++ b/src/vapi/mpv.vapi
@@ -59,7 +59,7 @@ namespace Mpv {
 
         public Error set_property_flag (string name, bool value) {
             int flag = value ? 1 : 0;
-            return this.set_property (name, Format.INT64, &flag);
+            return this.set_property (name, Format.FLAG, &flag);
         }
 
         [CCode (cname = "mpv_command")]