diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 0fae2dfe9fb..4a02ec178e6 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -4247,6 +4247,14 @@ order (MRO) for bases """
         with self.assertRaises(TypeError):
             str.__add__(fake_str, "abc")
 
+    def test_repr_as_str(self):
+        # Issue #11603: crash or infinite loop when rebinding __str__ as
+        # __repr__.
+        class Foo:
+            pass
+        Foo.__repr__ = Foo.__str__
+        foo = Foo()
+        str(foo)
 
 class DictProxyTests(unittest.TestCase):
     def setUp(self):
diff --git a/Misc/NEWS b/Misc/NEWS
index 28f8d0ae189..8b7e02c237e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -225,6 +225,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #11603: Fix a crash when __str__ is rebound as __repr__.  Patch by
+  Andreas Stührk.
+
 - Issue #11321: Fix a crash with multiple imports of the _pickle module when
   embedding Python.  Patch by Andreas Stührk.
 
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 1642dade540..d80b594e9a6 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2968,7 +2968,7 @@ object_str(PyObject *self)
     unaryfunc f;
 
     f = Py_TYPE(self)->tp_repr;
-    if (f == NULL)
+    if (f == NULL || f == object_str)
         f = object_repr;
     return f(self);
 }