diff --git a/src/machine/execute.rs b/src/machine/execute.rs
index 3e1de0e5..a11cb6a7 100644
--- a/src/machine/execute.rs
+++ b/src/machine/execute.rs
@@ -17,16 +17,13 @@ impl Execute for Machine {
     fn tick(&mut self) {
         let op = self.decode();
         let mut s = self.stack();
-        println!("Operation: {:?}", op);
 
         // Should we jump to a different instruction?
         let mut jump: Option<u16> = None;
 
         match op {
-            I::None => {}
-
-            I::Push(v) => { self.push(v); }
-            I::Pop => { self.pop(); }
+            I::Push(v) => { s.push(v).expect("push error"); }
+            I::Pop => { s.pop().expect("pop error"); }
 
             // Addition, subtraction, multiplication and division.
             I::Add => s.apply_two(|a, b| a + b),
@@ -52,36 +49,37 @@ impl Execute for Machine {
             I::Jump(addr) => self.reg.set(PC, addr),
 
             I::JumpZero(addr) => {
-                if self.pop() == 0 {
+                if s.pop().unwrap() == 0 {
                     jump = Some(addr);
                 }
             }
 
             I::JumpNotZero(addr) => {
-                if self.pop() != 0 {
+                if s.pop().unwrap() != 0 {
                     jump = Some(addr);
                 }
             }
 
             I::Dup => {
                 let v = s.peek();
-                self.push(v);
+                s.push(v).unwrap();
             }
 
             I::Swap => {
-                let a = self.pop();
-                let b = self.pop();
+                let a = s.pop().unwrap();
+                let b = s.pop().unwrap();
 
-                self.push(a);
-                self.push(b);
+                s.push(a).unwrap();
+                s.push(b).unwrap();
             }
 
             I::Over => {
                 let v = s.get(1);
-                self.push(v);
+                s.push(v).unwrap();
             }
 
             I::Halt => {}
+            I::None => {}
         };
 
         if let Some(addr) = jump {
diff --git a/src/machine/mod.rs b/src/machine/mod.rs
index 2740584f..424b9030 100644
--- a/src/machine/mod.rs
+++ b/src/machine/mod.rs
@@ -17,40 +17,24 @@ pub struct Machine {
 impl Machine {
     /// Creates a new machine.
     pub fn new() -> Machine {
-        let mem = Memory::new();
-        let reg = Registers::new();
-
-        Machine { mem, reg }
+        Machine { mem: Memory::new(), reg: Registers::new() }
     }
 
     /// Returns a stack manager for the current machine.
-    fn stack(&mut self) -> StackManager {
+    pub fn stack(&mut self) -> StackManager {
         StackManager::new(&mut self.mem, &mut self.reg)
     }
-
-    /// Pops a value from the stack.
-    fn pop(&mut self) -> u16 {
-        self.stack().pop().unwrap()
-    }
-
-    /// Pushes a value onto the stack.
-    fn push(&mut self, value: u16) {
-        self.stack().push(value).unwrap();
-    }
-
-    pub fn load(&mut self, ops: Vec<I>) {
-        // Append a [halt] instruction to the code.
-        let mut code = ops.clone();
-        code.push(I::Halt);
-
-        self.mem.load_code(code);
-    }
 }
 
 impl From<Vec<Instruction>> for Machine {
     fn from(code: Vec<Instruction>) -> Self {
         let mut m = Machine::new();
-        m.load(code);
+
+        // Add a halt instruction to the end of the code.
+        let mut code = code.clone();
+        code.push(I::Halt);
+
+        m.mem.load_code(code);
         m
     }
 }