diff --git a/src/kernel/exception.rs b/src/kernel/exception.rs
index 17599f2..b020f6e 100644
--- a/src/kernel/exception.rs
+++ b/src/kernel/exception.rs
@@ -44,7 +44,7 @@ pub const SC_DEBUG: u8 = 34;
 pub const CONSOLE_OUTPUT: u8 = 1;
 
 // todo : returns new types, not just machine errors and machine ok
-pub fn call(exception: ExceptionType, machine: &mut Machine, system: &mut System) -> Result<MachineOk, MachineError> {
+pub fn call(exception: &ExceptionType, machine: &mut Machine, system: &mut System) -> Result<MachineOk, MachineError> {
 
     match exception {
         ExceptionType::NoException => todo!(),
@@ -66,10 +66,10 @@ fn syscall(machine: &mut Machine, system: &mut System) -> Result<MachineOk, Mach
         SC_SHUTDOWN => Ok(MachineOk::Shutdown),
         SC_EXIT => {
             let th = match &system.get_thread_manager().g_current_thread {
-                Some(th) => th,
+                Some(th) => th.clone(),
                 None => Err("Current thread is None")?
             };
-            system.get_thread_manager().thread_finish(machine, *th);
+            system.get_thread_manager().thread_finish(machine, th);
             Ok(MachineOk::Ok)
         },
         SC_EXEC => todo!(),
diff --git a/src/simulator/machine.rs b/src/simulator/machine.rs
index 9baf651..166fbce 100644
--- a/src/simulator/machine.rs
+++ b/src/simulator/machine.rs
@@ -34,6 +34,7 @@ use super::error::MachineOk;
 /// Textual names of the exceptions that can be generated by user program
 /// execution, for debugging purpose.
 /// todo: is this really supposed to stand in machine.rs?
+#[derive(Debug)]
 pub enum ExceptionType {
 	/// Everything ok
 	NoException,
@@ -229,7 +230,7 @@ impl Machine {
 	pub fn raise_exception(&mut self, exception: ExceptionType, address : u64, system: &mut System) -> Result<MachineOk, MachineError>{
 		self.set_status(MachineStatus::SystemMode);
 		// Handle the interruption
-		match exception::call(exception, self, system) {
+		match exception::call(&exception, self, system) {
 			Ok(MachineOk::Shutdown) => {
 				self.set_status(MachineStatus::UserMode);
 				return Ok(MachineOk::Shutdown);