diff --git a/tests/integration.rs b/tests/integration.rs
index ed9ff18..1fd07d3 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -2296,4 +2296,9 @@ fn test_builtin_functions_context() {
 fn test_hex() {
     assert_eq!(eval("0x3"), Ok(Value::Int(3)));
     assert_eq!(eval("0xFF"), Ok(Value::Int(255)));
+    assert_eq!(eval("-0xFF"), Ok(Value::Int(-255)));
+    assert_eq!(
+        eval("0x"),
+        Err(EvalexprError::VariableIdentifierNotFound("0x".into()))
+    );
 }