diff --git a/include/sys/avl_impl.h b/include/sys/avl_impl.h
index f577ecd42f..c464a62a1c 100644
--- a/include/sys/avl_impl.h
+++ b/include/sys/avl_impl.h
@@ -147,7 +147,9 @@ struct avl_tree {
 	int (*avl_compar)(const void *, const void *);
 	size_t avl_offset;		/* offsetof(type, avl_link_t field) */
 	ulong_t avl_numnodes;		/* number of nodes in the tree */
-	size_t avl_size;		/* sizeof user type struct */
+#ifndef _KERNEL
+	size_t avl_pad;			/* For backwards ABI compatibility. */
+#endif
 };
 
 
diff --git a/module/avl/avl.c b/module/avl/avl.c
index 1a95092bc2..3d36d4c87e 100644
--- a/module/avl/avl.c
+++ b/module/avl/avl.c
@@ -875,7 +875,6 @@ avl_swap(avl_tree_t *tree1, avl_tree_t *tree2)
 
 	ASSERT3P(tree1->avl_compar, ==, tree2->avl_compar);
 	ASSERT3U(tree1->avl_offset, ==, tree2->avl_offset);
-	ASSERT3U(tree1->avl_size, ==, tree2->avl_size);
 
 	temp_node = tree1->avl_root;
 	temp_numnodes = tree1->avl_numnodes;
@@ -903,7 +902,6 @@ avl_create(avl_tree_t *tree, int (*compar) (const void *, const void *),
 	tree->avl_compar = compar;
 	tree->avl_root = NULL;
 	tree->avl_numnodes = 0;
-	tree->avl_size = size;
 	tree->avl_offset = offset;
 }