diff --git a/src/main.zig b/src/main.zig
index baabf78..14645ec 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -13,6 +13,7 @@ const Chunk = struct {
     count: usize,
     capacity: usize,
     code: []u8,
+    lines: []usize,
     constants: ValueArray,
 
     pub fn new() Chunk {
@@ -20,6 +21,7 @@ const Chunk = struct {
             .count = 0,
             .capacity = 0,
             .code = &.{},
+            .lines = &.{},
             .constants = ValueArray.new(),
         };
     }
@@ -30,17 +32,20 @@ const Chunk = struct {
         self.count = 0;
         self.capacity = 0;
         self.code = &.{};
+        self.lines = &.{};
         self.constants = ValueArray.new();
     }
 
-    pub fn write(self: *Chunk, allocator: Allocator, byte: u8) !void {
+    pub fn write(self: *Chunk, allocator: Allocator, byte: u8, line: usize) !void {
         if (self.capacity < self.count + 1) {
             const old_capacity = self.capacity;
             self.capacity = utils.grow_capacity(old_capacity);
             self.code = try allocator.realloc(self.code, self.capacity);
+            self.lines = try allocator.realloc(self.lines, self.capacity);
         }
 
         self.code[self.count] = byte;
+        self.lines[self.count] = line;
         self.count += 1;
     }
 
@@ -61,6 +66,12 @@ const Chunk = struct {
     pub fn dissassemble_instruction(self: Chunk, offset: usize) usize {
         debug.print("{x:0>4} ", .{offset});
 
+        if (offset > 0 and self.lines[offset] == self.lines[offset - 1]) {
+            debug.print("   | ", .{});
+        } else {
+            debug.print("{d:4} ", .{self.lines[offset]});
+        }
+
         const instruction = self.code[offset];
 
         switch (instruction) {
@@ -78,6 +89,7 @@ const Chunk = struct {
 
         if (self.capacity > 0) {
             allocator.free(self.code);
+            allocator.free(self.lines);
         }
     }
 
@@ -95,9 +107,9 @@ pub fn simple_instruction(opcode_name: []const u8, offset: usize) usize {
 
 pub fn constant_instruction(opcode_name: []const u8, chunk: Chunk, offset: usize) usize {
     const constant = chunk.code[offset + 1];
-    debug.print("{s:16} {d:4} ", .{ opcode_name, constant });
+    debug.print("{s:16} {d:4} '", .{ opcode_name, constant });
     values.print_value(chunk.constants.values[constant]);
-    debug.print("\n", .{});
+    debug.print("'\n", .{});
     return offset + 2;
 }
 
@@ -109,10 +121,10 @@ pub fn main() !void {
     var chunk = Chunk.new();
     try chunk.init(allocator);
 
-    try chunk.write(allocator, @intFromEnum(OpCode.OP_RETURN));
+    try chunk.write(allocator, @intFromEnum(OpCode.OP_RETURN), 123);
     const constant = try chunk.add_constant(allocator, 1.2);
-    try chunk.write(allocator, @intFromEnum(OpCode.OP_CONSTANT));
-    try chunk.write(allocator, @intCast(constant));
+    try chunk.write(allocator, @intFromEnum(OpCode.OP_CONSTANT), 123);
+    try chunk.write(allocator, @intCast(constant), 123);
 
     chunk.dissassemble("test chunk");
 
diff --git a/src/values.zig b/src/values.zig
index 7075031..53c6759 100644
--- a/src/values.zig
+++ b/src/values.zig
@@ -39,5 +39,5 @@ pub const ValueArray = struct {
 };
 
 pub fn print_value(value: Value) void {
-    debug.print("{any}", .{value});
+    debug.print("{d}", .{value});
 }