diff --git a/asm/assemble.go b/asm/assemble.go
index 0e9dca8..4fd6e3b 100644
--- a/asm/assemble.go
+++ b/asm/assemble.go
@@ -65,7 +65,7 @@ func assembleInstruction(in instruction) (*vm.Instruction, error) {
 	instr.OpCode = opCode
 
 	operands := in[1:]
-	pattern := operandsByOpCode[instr.OpCode]
+	pattern := vm.OperandsByOpCode[instr.OpCode]
 	if len(operands) != len(pattern) {
 		return nil, fmt.Errorf("Incorrect number of operands: expected %d, found %d\n", len(pattern), len(operands))
 	}
@@ -82,7 +82,7 @@ func assembleInstruction(in instruction) (*vm.Instruction, error) {
 	return instr, nil
 }
 
-func assembleOperand(op string, t operandType) (*vm.Operand, error) {
+func assembleOperand(op string, t vm.OperandNumericType) (*vm.Operand, error) {
 	op = strings.ToLower(op)
 	ret := &vm.Operand{}
 	numStr := ""
@@ -96,7 +96,7 @@ func assembleOperand(op string, t operandType) (*vm.Operand, error) {
 		ret.Type = vm.GlobalMemoryIndex
 		numStr = strings.TrimPrefix(op, "g")
 
-	case t == s || t == u || t == us:
+	case t == vm.OperandSigned || t == vm.OperandUnsigned || t == vm.OperandSignedOrUnsigned:
 		ret.Type = vm.Literal
 		numStr = op
 
@@ -105,14 +105,14 @@ func assembleOperand(op string, t operandType) (*vm.Operand, error) {
 	}
 
 	switch {
-	case t == s || (t == us && (strings.HasPrefix(numStr, "+") || strings.HasPrefix(numStr, "-"))):
+	case t == vm.OperandSigned || (t == vm.OperandSignedOrUnsigned && (strings.HasPrefix(numStr, "+") || strings.HasPrefix(numStr, "-"))):
 		num, err := strconv.ParseInt(numStr, 0, 64)
 		if err != nil {
 			return ret, errors.Wrapf(err, "While parsing operand value %s", numStr)
 		}
 		ret.Value = uint64(num)
 
-	case t == u || t == us || t == r:
+	case t == vm.OperandUnsigned || t == vm.OperandSignedOrUnsigned || t == vm.OperandReference:
 		num, err := strconv.ParseUint(numStr, 0, 64)
 		if err != nil {
 			return ret, errors.Wrapf(err, "While parsing operand value %s", numStr)
diff --git a/asm/disassemble.go b/asm/disassemble.go
index 2b3a3b6..7e37a47 100644
--- a/asm/disassemble.go
+++ b/asm/disassemble.go
@@ -44,7 +44,7 @@ func disassembleInstruction(in *vm.Instruction) (string, error) {
 		nameByOpCode[in.OpCode],
 	}
 
-	for i, t := range operandsByOpCode[in.OpCode] {
+	for i, t := range vm.OperandsByOpCode[in.OpCode] {
 		op, err := disassembleOperand(in.Operands[i], t)
 		if err != nil {
 			return "", err
@@ -58,7 +58,7 @@ func disassembleInstruction(in *vm.Instruction) (string, error) {
 	return encoded, nil
 }
 
-func disassembleOperand(op *vm.Operand, t operandType) (string, error) {
+func disassembleOperand(op *vm.Operand, t vm.OperandNumericType) (string, error) {
 	switch op.Type {
 	case vm.GlobalMemoryIndex:
 		return fmt.Sprintf("g%d", op.Value), nil
@@ -68,13 +68,13 @@ func disassembleOperand(op *vm.Operand, t operandType) (string, error) {
 
 	case vm.Literal:
 		switch t {
-		case u:
+		case vm.OperandUnsigned:
 			return fmt.Sprintf("%d", op.Value), nil
 
-		case s:
+		case vm.OperandSigned:
 			return fmt.Sprintf("%+d", int64(op.Value)), nil
 
-		case us:
+		case vm.OperandSignedOrUnsigned:
 			// Take our best guess
 			if op.Value > math.MaxInt64 {
 				return fmt.Sprintf("%+d", int64(op.Value)), nil
diff --git a/asm/opcodes.go b/asm/opcodes.go
index e8282b6..c3a3b9e 100644
--- a/asm/opcodes.go
+++ b/asm/opcodes.go
@@ -111,53 +111,3 @@ var nameByOpCode = map[vm.OpCodeType]string{
 	vm.OpRetT: "rett",
 	vm.OpRetF: "retf",
 }
-
-type operandType int
-
-const (
-	u  operandType = 0
-	s              = 1
-	us             = 2
-	r              = 3
-)
-
-var operandsByOpCode = map[vm.OpCodeType][]operandType{
-	vm.OpNop: []operandType{},
-
-	vm.OpMov:  []operandType{r, us},
-	vm.OpAdd:  []operandType{r, us},
-	vm.OpSub:  []operandType{r, us},
-	vm.OpMul:  []operandType{r, us},
-	vm.OpDivU: []operandType{r, u},
-	vm.OpDivS: []operandType{r, s},
-
-	vm.OpNot: []operandType{r},
-	vm.OpAnd: []operandType{r, u},
-	vm.OpOr:  []operandType{r, u},
-	vm.OpXor: []operandType{r, u},
-
-	vm.OpShR: []operandType{r, u},
-	vm.OpShL: []operandType{r, u},
-
-	vm.OpEq:   []operandType{us, us},
-	vm.OpLTU:  []operandType{u, u},
-	vm.OpLTS:  []operandType{s, s},
-	vm.OpGTU:  []operandType{u, u},
-	vm.OpGTS:  []operandType{s, s},
-	vm.OpLTEU: []operandType{u, u},
-	vm.OpLTES: []operandType{s, s},
-	vm.OpGTEU: []operandType{u, u},
-	vm.OpGTES: []operandType{s, s},
-
-	vm.OpJmp:  []operandType{s},
-	vm.OpJmpT: []operandType{s},
-	vm.OpJmpF: []operandType{s},
-
-	vm.OpCal:  []operandType{s},
-	vm.OpCalT: []operandType{s},
-	vm.OpCalF: []operandType{s},
-
-	vm.OpRet:  []operandType{},
-	vm.OpRetT: []operandType{},
-	vm.OpRetF: []operandType{},
-}
diff --git a/vm/opcode.go b/vm/opcode.go
index 20809b9..1e7546b 100644
--- a/vm/opcode.go
+++ b/vm/opcode.go
@@ -69,3 +69,53 @@ const (
 	OpReturnIfFalse = 0x00000802
 	OpRetF          = OpReturnIfFalse
 )
+
+type OperandNumericType int
+
+const (
+	OperandUnsigned         OperandNumericType = 0
+	OperandSigned                              = 1
+	OperandSignedOrUnsigned                    = 2
+	OperandReference                           = 3
+)
+
+var OperandsByOpCode = map[OpCodeType][]OperandNumericType{
+	OpNop: []OperandNumericType{},
+
+	OpMov:  []OperandNumericType{OperandReference, OperandSignedOrUnsigned},
+	OpAdd:  []OperandNumericType{OperandReference, OperandSignedOrUnsigned},
+	OpSub:  []OperandNumericType{OperandReference, OperandSignedOrUnsigned},
+	OpMul:  []OperandNumericType{OperandReference, OperandSignedOrUnsigned},
+	OpDivU: []OperandNumericType{OperandReference, OperandUnsigned},
+	OpDivS: []OperandNumericType{OperandReference, OperandSigned},
+
+	OpNot: []OperandNumericType{OperandReference},
+	OpAnd: []OperandNumericType{OperandReference, OperandUnsigned},
+	OpOr:  []OperandNumericType{OperandReference, OperandUnsigned},
+	OpXor: []OperandNumericType{OperandReference, OperandUnsigned},
+
+	OpShR: []OperandNumericType{OperandReference, OperandUnsigned},
+	OpShL: []OperandNumericType{OperandReference, OperandUnsigned},
+
+	OpEq:   []OperandNumericType{OperandSignedOrUnsigned, OperandSignedOrUnsigned},
+	OpLTU:  []OperandNumericType{OperandUnsigned, OperandUnsigned},
+	OpLTS:  []OperandNumericType{OperandSigned, OperandSigned},
+	OpGTU:  []OperandNumericType{OperandUnsigned, OperandUnsigned},
+	OpGTS:  []OperandNumericType{OperandSigned, OperandSigned},
+	OpLTEU: []OperandNumericType{OperandUnsigned, OperandUnsigned},
+	OpLTES: []OperandNumericType{OperandSigned, OperandSigned},
+	OpGTEU: []OperandNumericType{OperandUnsigned, OperandUnsigned},
+	OpGTES: []OperandNumericType{OperandSigned, OperandSigned},
+
+	OpJmp:  []OperandNumericType{OperandSigned},
+	OpJmpT: []OperandNumericType{OperandSigned},
+	OpJmpF: []OperandNumericType{OperandSigned},
+
+	OpCal:  []OperandNumericType{OperandSigned},
+	OpCalT: []OperandNumericType{OperandSigned},
+	OpCalF: []OperandNumericType{OperandSigned},
+
+	OpRet:  []OperandNumericType{},
+	OpRetT: []OperandNumericType{},
+	OpRetF: []OperandNumericType{},
+}