diff --git a/src/build/ast/Parse.go b/src/build/ast/Parse.go
index 674f121..760302e 100644
--- a/src/build/ast/Parse.go
+++ b/src/build/ast/Parse.go
@@ -61,7 +61,7 @@ func toASTNode(tokens token.List) (Node, error) {
 	switch {
 	case IsVariableDefinition(expr):
 		if len(expr.Children) < 2 {
-			return nil, errors.New(errors.MissingAssignValue, nil, expr.Token.End())
+			return nil, errors.New(errors.MissingOperand, nil, expr.Token.End())
 		}
 
 		name := expr.Children[0].Token
@@ -70,7 +70,7 @@ func toASTNode(tokens token.List) (Node, error) {
 
 	case IsAssignment(expr):
 		if len(expr.Children) < 2 {
-			return nil, errors.New(errors.MissingAssignValue, nil, expr.Token.End())
+			return nil, errors.New(errors.MissingOperand, nil, expr.Token.End())
 		}
 
 		name := expr.Children[0].Token
diff --git a/src/build/core/ExpressionToRegister.go b/src/build/core/ExpressionToRegister.go
index fade8b8..2f6cf6d 100644
--- a/src/build/core/ExpressionToRegister.go
+++ b/src/build/core/ExpressionToRegister.go
@@ -4,6 +4,7 @@ import (
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/ast"
 	"git.akyoto.dev/cli/q/src/build/cpu"
+	"git.akyoto.dev/cli/q/src/build/errors"
 	"git.akyoto.dev/cli/q/src/build/expression"
 )
 
@@ -23,6 +24,10 @@ func (f *Function) ExpressionToRegister(node *expression.Expression, register cp
 		return err
 	}
 
+	if len(node.Children) < 2 {
+		return errors.New(errors.MissingOperand, f.File, node.Token.End())
+	}
+
 	left := node.Children[0]
 	right := node.Children[1]
 	final := register
diff --git a/src/build/errors/CompileErrors.go b/src/build/errors/CompileErrors.go
index 13d5948..886d1f8 100644
--- a/src/build/errors/CompileErrors.go
+++ b/src/build/errors/CompileErrors.go
@@ -3,7 +3,7 @@ package errors
 var (
 	InvalidStatement    = &Base{"Invalid statement"}
 	InvalidExpression   = &Base{"Invalid expression"}
-	MissingAssignValue  = &Base{"Missing assignment value"}
+	MissingOperand      = &Base{"Missing operand"}
 	MissingMainFunction = &Base{"Missing main function"}
 	NotImplemented      = &Base{"Not implemented"}
 )
diff --git a/tests/errors/InvalidInstructionExpression.q b/tests/errors/InvalidInstructionExpression.q
new file mode 100644
index 0000000..c90293f
--- /dev/null
+++ b/tests/errors/InvalidInstructionExpression.q
@@ -0,0 +1,3 @@
+main() {
+	2+3
+}
\ No newline at end of file
diff --git a/tests/errors/MissingAssignValue.q b/tests/errors/MissingOperand.q
similarity index 100%
rename from tests/errors/MissingAssignValue.q
rename to tests/errors/MissingOperand.q
diff --git a/tests/errors/MissingOperand2.q b/tests/errors/MissingOperand2.q
new file mode 100644
index 0000000..9a030f4
--- /dev/null
+++ b/tests/errors/MissingOperand2.q
@@ -0,0 +1,3 @@
+main() {
+	syscall(2+)
+}
\ No newline at end of file
diff --git a/tests/errors_test.go b/tests/errors_test.go
index 6299be8..c3d2a11 100644
--- a/tests/errors_test.go
+++ b/tests/errors_test.go
@@ -19,17 +19,19 @@ var errs = []struct {
 	{"ExpectedFunctionParameters.q", errors.ExpectedFunctionParameters},
 	{"InvalidInstructionIdentifier.q", &errors.InvalidInstruction{Instruction: "abc"}},
 	{"InvalidInstructionNumber.q", &errors.InvalidInstruction{Instruction: "123"}},
+	{"InvalidInstructionExpression.q", &errors.InvalidInstruction{Instruction: "+"}},
 	{"InvalidExpression.q", errors.InvalidExpression},
 	{"InvalidOperator.q", &errors.InvalidOperator{Operator: "+++"}},
 	{"InvalidCharacter.q", &errors.InvalidCharacter{Character: "@"}},
 	{"InvalidCharacter2.q", &errors.InvalidCharacter{Character: "@"}},
 	{"InvalidCharacter3.q", &errors.InvalidCharacter{Character: "@"}},
-	{"MissingAssignValue.q", errors.MissingAssignValue},
 	{"MissingBlockEnd.q", errors.MissingBlockEnd},
 	{"MissingBlockStart.q", errors.MissingBlockStart},
 	{"MissingGroupEnd.q", errors.MissingGroupEnd},
 	{"MissingGroupStart.q", errors.MissingGroupStart},
 	{"MissingMainFunction.q", errors.MissingMainFunction},
+	{"MissingOperand.q", errors.MissingOperand},
+	{"MissingOperand2.q", errors.MissingOperand},
 	{"VariableAlreadyExists.q", &errors.VariableAlreadyExists{Name: "x"}},
 	{"UnknownIdentifier.q", &errors.UnknownIdentifier{Name: "x"}},
 	{"UnknownIdentifier2.q", &errors.UnknownIdentifier{Name: "x"}},