Obtained from:	https://gitlab.com/petsc/petsc/-/commit/87b0c9e1f4d83439f081eddd06cf19f419b1e4f9

--- conf/cyautodoc.py.orig	2025-01-29 22:17:46 UTC
+++ conf/cyautodoc.py
@@ -24,8 +24,9 @@ class ExpressionWriter(BaseExpressionWriter):
             self.visit(node.index)
         self.put(']')
 
-    def visit_UnicodeNode(self, node):
-        self.emit_string(node, '')
+    if hasattr(BaseExpressionWriter, 'emit_string'):
+        def visit_UnicodeNode(self, node):
+            self.emit_string(node, '')
 
 
 class AnnotationWriter(ExpressionWriter, BaseAnnotationWriter):
--- src/petsc4py/PETSc/petscdm.pxi.orig	2025-01-29 22:17:46 UTC
+++ src/petsc4py/PETSc/petscdm.pxi
@@ -236,9 +236,12 @@ cdef inline PetscInt asBoundary(object boundary,
                                 PetscDMBoundaryType *_z) except -1:
     cdef PetscInt dim = 0
     cdef object x=None, y=None, z=None
+    # Use `type(0)` instead of `int` to workaround
+    # Cython 3.1 failing to interpret `int` as a type
+    cdef type pyint = type(0)
     if boundary is None or \
        isinstance(boundary, str) or \
-       isinstance(boundary, int):
+       isinstance(boundary, pyint):
         _x[0] = _y[0] = _z[0] = asBoundaryType(boundary)
     else:
         _x[0] = _y[0] = _z[0] = DM_BOUNDARY_NONE
--- src/petsc4py/PETSc/petscis.pxi.orig	2025-01-29 22:17:46 UTC
+++ src/petsc4py/PETSc/petscis.pxi
@@ -181,28 +181,6 @@ cdef class _IS_buffer:
     def __exit__(self, *exc):
         return self.exit()
 
-    # buffer interface (legacy)
-
-    cdef Py_ssize_t getbuffer(self, void **p) except -1:
-        cdef PetscInt n = 0
-        if p != NULL:
-            self.acquire()
-            p[0] = <void*>self.data
-            n = self.size
-        elif self.iset != NULL:
-            CHKERR(ISGetLocalSize(self.iset, &n))
-        return <Py_ssize_t>(<size_t>n*sizeof(PetscInt))
-
-    def __getsegcount__(self, Py_ssize_t *lenp):
-        if lenp != NULL:
-            lenp[0] = self.getbuffer(NULL)
-        return 1
-
-    def __getreadbuffer__(self, Py_ssize_t idx, void **p):
-        if idx != 0: raise SystemError(
-            "accessing non-existent buffer segment")
-        return self.getbuffer(p)
-
     # NumPy array interface (legacy)
 
     property __array_interface__:
--- src/petsc4py/PETSc/petscvec.pxi.orig	2025-01-29 22:17:46 UTC
+++ src/petsc4py/PETSc/petscvec.pxi
@@ -573,35 +573,6 @@ cdef class _Vec_buffer:
     def __exit__(self, *exc):
         return self.exit()
 
-    # buffer interface (legacy)
-
-    cdef Py_ssize_t getbuffer(self, void **p) except -1:
-        cdef PetscInt n = 0
-        if p != NULL:
-            self.acquire()
-            p[0] = <void*>self.data
-            n = self.size
-        elif self.vec != NULL:
-            CHKERR(VecGetLocalSize(self.vec, &n))
-        return <Py_ssize_t>(<size_t>n*sizeof(PetscScalar))
-
-    def __getsegcount__(self, Py_ssize_t *lenp):
-        if lenp != NULL:
-            lenp[0] = self.getbuffer(NULL)
-        return 1
-
-    def __getreadbuffer__(self, Py_ssize_t idx, void **p):
-        if idx != 0: raise SystemError(
-            "accessing non-existent buffer segment")
-        return self.getbuffer(p)
-
-    def __getwritebuffer__(self, Py_ssize_t idx, void **p):
-        if idx != 0: raise SystemError(
-            "accessing non-existent buffer segment")
-        if self.readonly: raise TypeError(
-            "Object is not writable.")
-        return self.getbuffer(p)
-
     # NumPy array interface (legacy)
 
     property __array_interface__: