diff --git a/dissect/cstruct/expression.py b/dissect/cstruct/expression.py
index 774e376..1cc3c0a 100644
--- a/dissect/cstruct/expression.py
+++ b/dissect/cstruct/expression.py
@@ -299,4 +299,7 @@ def evaluate(self, context: dict[str, int] | None = None) -> int:
 
             self.evaluate_exp()
 
+        if len(self.queue) != 1:
+            raise ExpressionParserError("Invalid expression")
+
         return self.queue[0]
diff --git a/tests/test_expression.py b/tests/test_expression.py
index 11f67e4..bad5fb5 100644
--- a/tests/test_expression.py
+++ b/tests/test_expression.py
@@ -94,6 +94,7 @@ def test_expression(expression: str, answer: int) -> None:
         ("-", ExpressionParserError, "Invalid expression: not enough operands"),
         ("(", ExpressionParserError, "Invalid expression"),
         (")", ExpressionParserError, "Invalid expression"),
+        (" ", ExpressionParserError, "Invalid expression"),
         ("()", ExpressionParserError, "Parser expected an expression, instead received empty parenthesis. Index: 1"),
         ("0()", ExpressionParserError, "Parser expected sizeof or an arethmethic operator instead got: '0'"),
         ("sizeof)", ExpressionParserError, "Invalid sizeof operation"),