diff --git a/tests/test_utils_eval.py b/tests/test_utils_eval.py
index a452c16f..ad9ffb60 100644
--- a/tests/test_utils_eval.py
+++ b/tests/test_utils_eval.py
@@ -23,7 +23,7 @@ from slic.utils.eval import *
     ("3 + +4", 7),
     ("3 + -4", -1),
     ("True + 1", 2),
-    ('string', 'string'),
+    ("'string'", 'string'),
     ("1e1000 * 1e1000", float("inf")), 
     ("'a' + 'b'", "ab")     # string concatenation supported !!!
 ])