diff --git a/src/chunk.zig b/src/chunk.zig
index 491d52b..db17a34 100644
--- a/src/chunk.zig
+++ b/src/chunk.zig
@@ -8,6 +8,7 @@ const AllOpcodes = struct {
     pub Constant: u8 = 0,
     pub ConstantLong: u8 = 1,
     pub Return: u8 = 2,
+    pub Negate: u8 = 3,
 };
 
 pub const OpCode = AllOpcodes{};
@@ -148,6 +149,8 @@ pub const Chunk = struct {
                 self,
                 index,
             );
+        } else if (instruction == OpCode.Negate) {
+            return try simpleInstruction(stdout, "OP_NEGATE", index);
         } else {
             try stdout.print("Unknown opcode: {}\n", instruction);
             return index + 1;
diff --git a/src/main.zig b/src/main.zig
index 1d4bdc7..d493e1a 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -117,6 +117,7 @@ pub fn main() !void {
     //try chk.write(chunk.OpCode.Return);
 
     var constant = try chk.writeConstant(1.2, 123);
+    try chk.write(chunk.OpCode.Negate, 123);
     try chk.write(chunk.OpCode.Return, 123);
 
     var vmach = vm.VM.init(stdout, &chk, true);
diff --git a/src/vm.zig b/src/vm.zig
index b4243b8..5d74853 100644
--- a/src/vm.zig
+++ b/src/vm.zig
@@ -107,6 +107,8 @@ pub const VM = struct {
                     try self.stdout.print("\n");
                     return InterpretResult.Ok;
                 },
+
+                chunk.OpCode.Negate => self.push(-self.pop()),
                 else => blk: {
                     std.debug.warn("Unknown instruction: {x}\n", instruction);
                     return InterpretResult.RuntimeError;