diff --git a/src/runtime.rs b/src/runtime.rs
index 02ef184..fa4ade6 100644
--- a/src/runtime.rs
+++ b/src/runtime.rs
@@ -49,12 +49,12 @@ pub(super) struct RunState {
     _psr: u16,
 }
 
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Default)]
 pub(super) enum RunFlag {
     N = 0b100,
+    #[default]
     Z = 0b010,
     P = 0b001,
-    Uninit = 0b000,
 }
 
 impl RunEnvironment {
@@ -118,7 +118,7 @@ impl RunEnvironment {
                 mem: Box::new(mem),
                 pc: orig as u16,
                 reg: [0, 0, 0, 0, 0, 0, 0, 0xFDFF],
-                flag: RunFlag::Uninit,
+                flag: RunFlag::default(),
                 _psr: 0,
             },
             debugger: None,