diff --git a/src/makefun/main.py b/src/makefun/main.py
index 22cd52e..e682155 100644
--- a/src/makefun/main.py
+++ b/src/makefun/main.py
@@ -466,7 +466,7 @@ def _signature_symbol_needs_protection(symbol, evaldict):
     :param symbol:
     :return:
     """
-    if symbol is not None and symbol is not Parameter.empty and not isinstance(symbol, TYPES_WITH_SAFE_REPR):
+    if symbol is not None and symbol is not Parameter.empty and type(symbol) not in TYPES_WITH_SAFE_REPR:
         try:
             # check if the repr() of the default value is equal to itself.
             return eval(repr(symbol), evaldict) != symbol  # noqa  # we cannot use ast.literal_eval, too restrictive
diff --git a/tests/test_issues.py b/tests/test_issues.py
index d314d6e..ed32a9b 100644
--- a/tests/test_issues.py
+++ b/tests/test_issues.py
@@ -280,3 +280,19 @@ def test_issue_91():
     """This test should work also in python 2 ! """
     assert is_identifier("_results_bag")
     assert is_identifier("hello__bag")
+
+
+def test_issue_98():
+    class A(str):
+        def __str__(self):
+            return 'custom str'
+
+        def __repr__(self):
+            return 'custom repr'
+
+    def foo(a=A()):
+        pass
+
+    @wraps(foo)
+    def test(*args, **kwargs):
+        return foo(*args, **kwargs)