diff --git a/src/simulator/machine.rs b/src/simulator/machine.rs
index 57f4550..d63ea1e 100644
--- a/src/simulator/machine.rs
+++ b/src/simulator/machine.rs
@@ -44,7 +44,7 @@ impl Machine {
 	/// - **address** in the memory to read
 	pub fn read_memory(machine : &mut Machine, size : i32, address : usize) -> u64 {
 		if size != 1 && size != 2 && size != 4 && size != 8 {
-			println!("ERROR read_memory : wrong size parameter {}, must be (1, 2, 4 or 8)", size);
+			panic!("ERROR read_memory : wrong size parameter {}, must be (1, 2, 4 or 8)", size);
 		}
 
 		let mut ret : u64 = machine.main_memory[address] as u64;
@@ -379,5 +379,5 @@ impl Machine {
 #[cfg(test)]
  mod test {
  	use super::Machine;
- 
+	
  }