diff --git a/c/CHANGELOG.rst b/c/CHANGELOG.rst
index e094f53774..a4eb87e473 100644
--- a/c/CHANGELOG.rst
+++ b/c/CHANGELOG.rst
@@ -4,6 +4,9 @@
 
 **Breaking changes**
 
+- The ``tables`` argument to ``tsk_treeseq_init`` is no longer ``const``, to allow for future no-copy tree sequence creation.
+  (:user:`benjeffery`, :issue:`1718`, :pr:`1719`)
+
 **Features**
 
 - The default behaviour for table size growth is now to double the current size of the table.
diff --git a/c/tskit/trees.c b/c/tskit/trees.c
index 621af66bbf..caa1a31652 100644
--- a/c/tskit/trees.c
+++ b/c/tskit/trees.c
@@ -341,7 +341,7 @@ tsk_treeseq_init_nodes(tsk_treeseq_t *self)
  */
 int TSK_WARN_UNUSED
 tsk_treeseq_init(
-    tsk_treeseq_t *self, const tsk_table_collection_t *tables, tsk_flags_t options)
+    tsk_treeseq_t *self, tsk_table_collection_t *tables, tsk_flags_t options)
 {
     int ret = 0;
     tsk_id_t num_trees;
diff --git a/c/tskit/trees.h b/c/tskit/trees.h
index 811195c99b..448802ec88 100644
--- a/c/tskit/trees.h
+++ b/c/tskit/trees.h
@@ -225,7 +225,7 @@ typedef struct {
 @{
 */
 int tsk_treeseq_init(
-    tsk_treeseq_t *self, const tsk_table_collection_t *tables, tsk_flags_t options);
+    tsk_treeseq_t *self, tsk_table_collection_t *tables, tsk_flags_t options);
 
 int tsk_treeseq_load(tsk_treeseq_t *self, const char *filename, tsk_flags_t options);
 int tsk_treeseq_loadf(tsk_treeseq_t *self, FILE *file, tsk_flags_t options);