diff --git a/src/sage/graphs/base/sparse_graph.pxd b/src/sage/graphs/base/sparse_graph.pxd
index 37f4e031f0a..d2d8ef5484b 100644
--- a/src/sage/graphs/base/sparse_graph.pxd
+++ b/src/sage/graphs/base/sparse_graph.pxd
@@ -9,6 +9,7 @@
 #*****************************************************************************
 
 from .c_graph cimport CGraph, CGraphBackend
+cimport cython
 
 cdef struct SparseGraphLLNode:
     int label
@@ -22,6 +23,7 @@ cdef struct SparseGraphBTNode:
     SparseGraphBTNode *left
     SparseGraphBTNode *right
 
+@cython.final
 cdef class SparseGraph(CGraph):
     cdef int hash_length
     cdef int hash_mask