diff --git a/gemma/src/chip8/video.rs b/gemma/src/chip8/video.rs
index c9b5d7d..75ba19d 100644
--- a/gemma/src/chip8/video.rs
+++ b/gemma/src/chip8/video.rs
@@ -55,7 +55,7 @@ impl Chip8Video {
         } else {
             trace!("NOT TOGGLING");
         }
-        self.memory[effective_address as usize] = new_value;
+        self.memory[effective_address as usize] = new_value ^ old_value;
         self.to_owned()
     }