diff --git a/oden-script/src/parser.rs b/oden-script/src/parser.rs
index 2753a872..bc98d520 100644
--- a/oden-script/src/parser.rs
+++ b/oden-script/src/parser.rs
@@ -599,6 +599,18 @@ mod tests {
         "cannot apply unary operator '-' to expression of type 'string'"
     );
 
+    test_type_error_expr!(
+        add_string_number,
+        "'what?' + 5",
+        "cannot apply binary operator '+' to expressions of type 'string' (on the left) and 'f64' (on the right)"
+    );
+
+    test_type_error_expr!(
+        add_number_string,
+        "5 + 'what?'",
+        "cannot apply binary operator '+' to expressions of type 'f64' (on the left) and 'string' (on the right)"
+    );
+
     test_type_error_expr!(
         errors_propagate_do_not_duplicate,
         "!'hello' / 27 * -('what?') + 23",