diff --git a/src/cpu.rs b/src/cpu.rs
index ac20718..b0a2344 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -97,7 +97,7 @@ impl Cpu {
         self.bus.read_word(addr)
     }
 
-    pub fn read_byte(&mut self, addr: u16) -> u8 {
+    pub fn read_byte(&self, addr: u16) -> u8 {
         self.bus.read_byte(addr)
     }