diff --git a/lib/wp/private.h b/lib/wp/private.h
index 792bb977..0513ab7f 100644
--- a/lib/wp/private.h
+++ b/lib/wp/private.h
@@ -44,10 +44,6 @@ WpSpaPod * wp_spa_pod_new_control_wrap_const (guint32 offset, guint32 type,
     const struct spa_pod *pod);
 const struct spa_pod *wp_spa_pod_get_spa_pod (const WpSpaPod *self);
 
-/* session item */
-
-void wp_session_item_set_parent (WpSessionItem *self, WpSessionItem *parent);
-
 G_END_DECLS
 
 #endif
diff --git a/lib/wp/session-bin.c b/lib/wp/session-bin.c
index 61f4f571..7945f9ee 100644
--- a/lib/wp/session-bin.c
+++ b/lib/wp/session-bin.c
@@ -13,7 +13,6 @@
 
 #define G_LOG_DOMAIN "wp-sb"
 
-#include "private.h"
 #include "session-bin.h"
 
 typedef struct _WpSessionBinPrivate WpSessionBinPrivate;
diff --git a/lib/wp/session-item.c b/lib/wp/session-item.c
index 20d819cd..df57796a 100644
--- a/lib/wp/session-item.c
+++ b/lib/wp/session-item.c
@@ -14,12 +14,14 @@
 #define G_LOG_DOMAIN "wp-si"
 
 #include "session-item.h"
+#include "core.h"
 #include "debug.h"
 #include "error.h"
 #include "wpenums.h"
-#include "private.h"
 #include "private/impl-endpoint.h"
 
+#include <spa/utils/defs.h>
+
 struct _WpSiTransition
 {
   WpTransition parent;
@@ -450,11 +452,10 @@ wp_session_item_get_parent (WpSessionItem * self)
 /**
  * wp_session_item_set_parent:
  * @self: the session item
+ * @parent: (transfer none): the parent item
  *
- * Gets the item's parent, which is the #WpSessionBin this item has been added
- * to, or NULL if the item does not belong to a session bin.
- *
- * Returns: (nullable) (transfer full): the item's parent.
+ * Private API.
+ * Sets the item's parent; used internally by #WpSessionBin.
  */
 void
 wp_session_item_set_parent (WpSessionItem *self, WpSessionItem *parent)
diff --git a/lib/wp/session-item.h b/lib/wp/session-item.h
index ed78549a..b64cba82 100644
--- a/lib/wp/session-item.h
+++ b/lib/wp/session-item.h
@@ -123,6 +123,9 @@ void wp_session_item_reset (WpSessionItem * self);
 WP_API
 WpSessionItem * wp_session_item_get_parent (WpSessionItem * self);
 
+WP_PRIVATE_API
+void wp_session_item_set_parent (WpSessionItem *self, WpSessionItem *parent);
+
 /* flags */
 
 WP_API