diff --git a/src/fox32.pest b/src/fox32.pest
index 1d30191..47022cc 100644
--- a/src/fox32.pest
+++ b/src/fox32.pest
@@ -80,7 +80,7 @@ instruction = {
 }
 
 instruction_conditional = {
-    instruction_zero          |
+    instruction_zero ~ size? |
     instruction_one ~ size? ~ operand |
     instruction_two ~ size? ~ operand ~ "," ~ operand
 }
diff --git a/src/main.rs b/src/main.rs
index de293dc..ecbcce4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -244,6 +244,7 @@ enum LabelKind {
 #[derive(PartialEq, Debug, Clone)]
 enum AstNode {
     OperationZero {
+        size: Size,
         condition: Condition,
         instruction: InstructionZero,
     },
@@ -729,7 +730,15 @@ fn parse_instruction(pair: pest::iterators::Pair<Rule>) -> AstNode {
             let mut inner_pair = pair.into_inner();
             let instruction_conditional_pair = inner_pair.next().unwrap();
             match instruction_conditional_pair.as_rule() {
-                Rule::instruction_zero => parse_instruction_zero(instruction_conditional_pair, condition),
+                Rule::instruction_zero => {
+                    if let Some(inner) = inner_pair.peek() {
+                        if inner.as_rule() == Rule::size {
+                            size = parse_size(&inner_pair.next().unwrap());
+                        }
+                    }
+                    *CURRENT_SIZE.lock().unwrap() = size;
+                    parse_instruction_zero(instruction_conditional_pair, size, condition)
+                }
                 Rule::instruction_one => {
                     if inner_pair.peek().unwrap().as_rule() == Rule::size {
                         size = parse_size(&inner_pair.next().unwrap());
@@ -859,8 +868,9 @@ fn parse_operand(mut pair: pest::iterators::Pair<Rule>, is_pointer: bool) -> Ast
     }
 }
 
-fn parse_instruction_zero(pair: pest::iterators::Pair<Rule>, condition: Condition) -> AstNode {
+fn parse_instruction_zero(pair: pest::iterators::Pair<Rule>, size: Size, condition: Condition) -> AstNode {
     AstNode::OperationZero {
+        size: size,
         condition: condition,
         instruction: match pair.as_str() {
             "nop"  => InstructionZero::Nop,
@@ -1044,17 +1054,17 @@ fn size_to_byte(size: &Size) -> u8 {
 
 fn instruction_to_byte(node: &AstNode) -> u8 {
     match node {
-        AstNode::OperationZero {instruction, ..} => {
+        AstNode::OperationZero {size, instruction, ..} => {
             match instruction {
-                InstructionZero::Nop  => 0x00 | size_to_byte(&Size::Word),
-                InstructionZero::Halt => 0x10 | size_to_byte(&Size::Word),
-                InstructionZero::Brk  => 0x20 | size_to_byte(&Size::Word),
-                InstructionZero::Ret  => 0x2A | size_to_byte(&Size::Word),
-                InstructionZero::Reti => 0x3A | size_to_byte(&Size::Word),
-                InstructionZero::Ise  => 0x0C | size_to_byte(&Size::Word),
-                InstructionZero::Icl  => 0x1C | size_to_byte(&Size::Word),
-                InstructionZero::Mse  => 0x0D | size_to_byte(&Size::Word),
-                InstructionZero::Mcl  => 0x1D | size_to_byte(&Size::Word),
+                InstructionZero::Nop  => 0x00 | size_to_byte(size),
+                InstructionZero::Halt => 0x10 | size_to_byte(size),
+                InstructionZero::Brk  => 0x20 | size_to_byte(size),
+                InstructionZero::Ret  => 0x2A | size_to_byte(size),
+                InstructionZero::Reti => 0x3A | size_to_byte(size),
+                InstructionZero::Ise  => 0x0C | size_to_byte(size),
+                InstructionZero::Icl  => 0x1C | size_to_byte(size),
+                InstructionZero::Mse  => 0x0D | size_to_byte(size),
+                InstructionZero::Mcl  => 0x1D | size_to_byte(size),
             }
         }
         AstNode::OperationOne {size, instruction, ..} => {