diff --git a/src/instruction.rs b/src/instruction.rs
index cedb35d..2746faf 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -1,6 +1,7 @@
 #[derive (Debug, PartialEq)]
 pub enum Instruction {
 	Add (u8, u8, u8),
+	AddI (u8, u8, i8),
 	
 	Call (u8, u8, u8),
 	Closure (u8, u32),
diff --git a/src/loader.rs b/src/loader.rs
index 712527b..a0fad1a 100644
--- a/src/loader.rs
+++ b/src/loader.rs
@@ -71,6 +71,11 @@ fn i_sb (buf: [u8; 4]) -> Option <i8> {
 	i8::try_from (i32::try_from (b).ok ()? - 127).ok ()
 }
 
+fn i_sc (buf: [u8; 4]) -> Option <i8> {
+	let c = buf [3];
+	i8::try_from (i32::try_from (c).ok ()? - 127).ok ()
+}
+
 pub fn parse_inst (buf: [u8; 4]) -> Option <Inst>
 {
 	let opcode = buf [0] & 0x7f;
@@ -79,6 +84,7 @@ pub fn parse_inst (buf: [u8; 4]) -> Option <Inst>
 	let b = buf [2];
 	let ax = a as u32 + ((b as u32) << 8);
 	let c = buf [3];
+	let s_c = c - 0x80;
 	let bx = 
 		(((buf [1] >> 7) as u32) << 0) | 
 		((buf [2] as u32) << 1) |
@@ -104,6 +110,7 @@ pub fn parse_inst (buf: [u8; 4]) -> Option <Inst>
 		0x11 => Inst::SetI (a, b, c, k),
 		0x12 => Inst::SetField (a, b, c, k),
 		0x13 => Inst::NewTable (a),
+		0x15 => Inst::AddI (a, b, i_sc (buf)?),
 		0x18 => Inst::MulK (a, b, c),
 		0x19 => Inst::ModK (a, b, c),
 		0x22 => Inst::Add (a, b, c),
diff --git a/src/state.rs b/src/state.rs
index 40d85f8..563eee2 100644
--- a/src/state.rs
+++ b/src/state.rs
@@ -178,6 +178,20 @@ impl <'a> State <'a> {
 				
 				*self.reg_mut (*a) = x;
 			},
+			Instruction::AddI (a, b, s_c) => {
+				let v_b = self.reg (*b);
+				
+				let x = if let Some (v_b) = v_b.as_int () 
+				{
+					Value::from (v_b + *s_c as i64)
+				}
+				else {
+					let v_b = v_b.as_float ().unwrap_or_else (|| panic! ("{v_b}"));
+					Value::from (v_b + f64::from (*s_c))
+				};
+				
+				*self.reg_mut (*a) = x;
+			},
 			Instruction::Call (a, b, _c) => {
 				let b = usize::from (*b);