diff --git a/docs/changes.rst b/docs/changes.rst
index f13fb94..ee091d0 100644
--- a/docs/changes.rst
+++ b/docs/changes.rst
@@ -8,6 +8,9 @@ Version 1.17.1
 
 * Due to GitHub actions changes, binary wheels were missing for macOS Intel.
 
+* Not implemented error for `__reduce__()` on `ObjectProxy` was incorrectly
+  displaying the error as being on `__reduce_ex__()`.
+
 Version 1.17.0
 --------------
 
diff --git a/src/wrapt/_wrappers.c b/src/wrapt/_wrappers.c
index 433af1b..7f85855 100644
--- a/src/wrapt/_wrappers.c
+++ b/src/wrapt/_wrappers.c
@@ -1253,7 +1253,7 @@ static PyObject *WraptObjectProxy_reduce(
         WraptObjectProxyObject *self, PyObject *args, PyObject *kwds)
 {
     PyErr_SetString(PyExc_NotImplementedError,
-                    "object proxy must define __reduce_ex__()");
+                    "object proxy must define __reduce__()");
 
     return NULL;
 }
diff --git a/src/wrapt/wrappers.py b/src/wrapt/wrappers.py
index f70ee79..62da8a3 100644
--- a/src/wrapt/wrappers.py
+++ b/src/wrapt/wrappers.py
@@ -440,7 +440,7 @@ def __deepcopy__(self, memo):
 
     def __reduce__(self):
         raise NotImplementedError(
-                'object proxy must define __reduce_ex__()')
+                'object proxy must define __reduce__()')
 
     def __reduce_ex__(self, protocol):
         raise NotImplementedError(