This is handled as well by the generic of Homset.__reduce__ method,

and the latter takes care of setting check=False as needed.

Author: nthiery

src/sage/modular/abvar/homspace.py

@@ -753,6 +753,18 @@ def __init__(self, A, gens=None, category=None):
             sage: sage.modular.abvar.homspace.EndomorphismSubring(J1(12345))
             Endomorphism ring of Abelian variety J1(12345) of dimension 5405473
 
+        :trac:`16275` removed the custom ``__reduce__`` method, since
+        :meth:`Homset.__reduce__` already implements appropriate
+        unpickling by construction::
+
+            sage: E.__reduce__.__module__
+            'sage.categories.homset'
+            sage: E.__reduce__()
+            (<function Hom at ...>,
+             (Abelian variety J0(11) of dimension 2,
+              Abelian variety J0(11) of dimension 2,
+              Category of modular abelian varieties over Rational Field,
+             False))
         """
         self._J = A.ambient_variety()
         self._A = A
@@ -776,15 +788,10 @@ def __init__(self, A, gens=None, category=None):
             self._gens = tuple([ self._get_matrix(g) for g in gens ])
         self._is_full_ring = gens is None
 
-    def __reduce__(self):
+    def __reduce__disabled(self):
         """
         Used in pickling.
 
-        EXAMPLES::
-
-            sage: E = J0(31).endomorphism_ring()
-            sage: loads(dumps(E)) == E
-            True
         """
         return End, (self.domain(),self.domain().category())