diff --git a/src/vm/obj/assemble.rs b/src/vm/obj/assemble.rs
index cc22ebe..5a186d6 100644
--- a/src/vm/obj/assemble.rs
+++ b/src/vm/obj/assemble.rs
@@ -196,7 +196,7 @@ impl Assemble for ValueDef {
 
     fn assemble(&self, _: &mut Asm) -> Result<Self::Out> {
         match self {
-            ValueDef::Int(x) => Ok(x.to_le_bytes().to_vec()),
+            ValueDef::Int(x, s) => Ok(x.to_le_bytes().iter().copied().take(s.len()).collect()),
             ValueDef::String(s) => {
                 let bytes = s.bytes();
                 let mut out = s.len().to_le_bytes().to_vec();
diff --git a/src/vm/obj/syn/ast.rs b/src/vm/obj/syn/ast.rs
index e222235..ad748a0 100644
--- a/src/vm/obj/syn/ast.rs
+++ b/src/vm/obj/syn/ast.rs
@@ -78,7 +78,7 @@ impl DataLine {
 
 #[derive(Debug, Clone)]
 pub enum ValueDef {
-    Int(u64),
+    Int(u64, IntSize),
     String(String),
     ZString(String),
 }
@@ -86,7 +86,7 @@ pub enum ValueDef {
 impl ValueDef {
     pub fn len(&self) -> usize {
         match self {
-            ValueDef::Int(_) => 8,
+            ValueDef::Int(_, s) => s.len(),
             ValueDef::String(s) => 8 + s.as_bytes().len(),
             ValueDef::ZString(s) => s.as_bytes().len() + 1,
         }
@@ -176,6 +176,17 @@ pub enum IntSize {
     U64,
 }
 
+impl IntSize {
+    pub fn len(&self) -> usize {
+        match self {
+            IntSize::U8 => 1,
+            IntSize::U16 => 2,
+            IntSize::U32 => 4,
+            IntSize::U64 => 8,
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum Inst {
     Add(Value, Value),
diff --git a/src/vm/obj/syn/lexer.l b/src/vm/obj/syn/lexer.l
index 7bd52ff..7ce1a8a 100644
--- a/src/vm/obj/syn/lexer.l
+++ b/src/vm/obj/syn/lexer.l
@@ -17,6 +17,10 @@ u8                                  "U8"
 u16                                 "U16"
 u32                                 "U32"
 u64                                 "U64"
+\.u8                                "U8_DEF"
+\.u16                               "U16_DEF"
+\.u32                               "U32_DEF"
+\.u64                               "U64_DEF"
 \.[iu](8|16|32|64)                  "INT_DEF"
 \.string                            "STR_DEF"
 \.zstring                           "ZSTR_DEF"
diff --git a/src/vm/obj/syn/parser.y b/src/vm/obj/syn/parser.y
index 6f2ced3..385ba4a 100644
--- a/src/vm/obj/syn/parser.y
+++ b/src/vm/obj/syn/parser.y
@@ -47,7 +47,10 @@ DataLine -> DataLine:
     ;
 
 ValueDef -> ValueDef:
-      'INT_DEF' Int { ValueDef::Int($2) }
+      'U8_DEF' Int { ValueDef::Int($2, IntSize::U8) }
+    | 'U16_DEF' Int { ValueDef::Int($2, IntSize::U16) }
+    | 'U32_DEF' Int { ValueDef::Int($2, IntSize::U32) }
+    | 'U64_DEF' Int { ValueDef::Int($2, IntSize::U64) }
     | 'STR_DEF' String { ValueDef::String($2) }
     | 'ZSTR_DEF' String { ValueDef::ZString($2) }
     ;