diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index aa99d198e436d5..06fd5cdc7be2a6 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1839,6 +1839,8 @@ are always available.  They are listed here in alphabetical order.
    Sentinel objects are truthy and compare equal only to themselves.  They are
    intended to be compared with the :keyword:`is` operator.
 
+   ``sentinel`` does not support subclassing.
+
    Shallow and deep copies of a sentinel object return the object itself.
 
    Sentinels are conventionally assigned to a variable with a matching name.
diff --git a/Include/internal/pycore_interp_structs.h b/Include/internal/pycore_interp_structs.h
index 01adadd1485189..fb810c82a5aa63 100644
--- a/Include/internal/pycore_interp_structs.h
+++ b/Include/internal/pycore_interp_structs.h
@@ -531,7 +531,7 @@ struct _py_func_state {
 
 /* For now we hard-code this to a value for which we are confident
    all the static builtin types will fit (for all builds). */
-#define _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES 202
+#define _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES 203
 #define _Py_MAX_MANAGED_STATIC_EXT_TYPES 10
 #define _Py_MAX_MANAGED_STATIC_TYPES \
     (_Py_MAX_MANAGED_STATIC_BUILTIN_TYPES + _Py_MAX_MANAGED_STATIC_EXT_TYPES)