diff --git a/the-super-tiny-compiler.js b/the-super-tiny-compiler.js
index 411fa54..55c351c 100755
--- a/the-super-tiny-compiler.js
+++ b/the-super-tiny-compiler.js
@@ -384,7 +384,7 @@ function tokenizer(input) {
   let current = 0;
 
   // And a `tokens` array for pushing our tokens to.
-  let tokens = [];
+  const tokens = [];
 
   // We start by creating a `while` loop where we are setting up our `current`
   // variable to be incremented as much as we want `inside` the loop.
@@ -436,7 +436,7 @@ function tokenizer(input) {
     //
     // So here we're just going to test for existence and if it does exist we're
     // going to just `continue` on.
-    let WHITESPACE = /\s/;
+    const WHITESPACE = /\s/;
     if (WHITESPACE.test(char)) {
       current++;
       continue;
@@ -451,7 +451,7 @@ function tokenizer(input) {
     //        Only two separate tokens
     //
     // So we start this off when we encounter the first number in a sequence.
-    let NUMBERS = /[0-9]/;
+    const NUMBERS = /[0-9]/;
     if (NUMBERS.test(char)) {
 
       // We're going to create a `value` string that we are going to push
@@ -511,7 +511,7 @@ function tokenizer(input) {
     //    ^^^
     //    Name token
     //
-    let LETTERS = /[a-z]/i;
+    const LETTERS = /[a-z]/i;
     if (LETTERS.test(char)) {
       let value = '';
 
@@ -606,7 +606,7 @@ function parser(tokens) {
       // We create a base node with the type `CallExpression`, and we're going
       // to set the name as the current token's value since the next token after
       // the open parenthesis is the name of the function.
-      let node = {
+      const node = {
         type: 'CallExpression',
         name: token.value,
         params: [],
@@ -674,7 +674,7 @@ function parser(tokens) {
 
   // Now, we're going to create our AST which will have a root which is a
   // `Program` node.
-  let ast = {
+  const ast = {
     type: 'Program',
     body: [],
   };
@@ -756,7 +756,7 @@ function traverser(ast, visitor) {
 
     // We start by testing for the existence of a method on the visitor with a
     // matching `type`.
-    let methods = visitor[node.type];
+    const methods = visitor[node.type];
 
     // If there is an `enter` method for this node type we'll call it with the
     // `node` and its `parent`.
@@ -859,7 +859,7 @@ function transformer(ast) {
 
   // We'll create a `newAst` which like our previous AST will have a program
   // node.
-  let newAst = {
+  const newAst = {
     type: 'Program',
     body: [],
   };
@@ -1026,10 +1026,10 @@ function codeGenerator(node) {
  */
 
 function compiler(input) {
-  let tokens = tokenizer(input);
-  let ast    = parser(tokens);
-  let newAst = transformer(ast);
-  let output = codeGenerator(newAst);
+  const tokens = tokenizer(input);
+  const ast    = parser(tokens);
+  const newAst = transformer(ast);
+  const output = codeGenerator(newAst);
 
   // and simply return the output!
   return output;