diff --git a/src/lv_objx/lv_btnm.c b/src/lv_objx/lv_btnm.c
index 6f284e92a..5ac473704 100644
--- a/src/lv_objx/lv_btnm.c
+++ b/src/lv_objx/lv_btnm.c
@@ -401,6 +401,9 @@ void lv_btnm_set_btn_width(const lv_obj_t * btnm, uint16_t btn_id, uint8_t width
 
 /**
  * Make the button matrix like a selector widget (only one button may be toggled at a time).
+ *
+ * Toggling must be enabled on the buttons you want to be selected with `lv_btnm_set_ctrl` or `lv_btnm_set_btn_ctrl_all`.
+ *
  * @param btnm Button matrix object
  * @param one_toggle Whether "one toggle" mode is enabled
  */
diff --git a/src/lv_objx/lv_btnm.h b/src/lv_objx/lv_btnm.h
index 09b5bb687..b02ab8417 100644
--- a/src/lv_objx/lv_btnm.h
+++ b/src/lv_objx/lv_btnm.h
@@ -170,6 +170,9 @@ void lv_btnm_set_btn_width(const lv_obj_t * btnm, uint16_t btn_id, uint8_t width
 
 /**
  * Make the button matrix like a selector widget (only one button may be toggled at a time).
+ *
+ * Toggling must be enabled on the buttons you want to be selected with `lv_btnm_set_ctrl` or `lv_btnm_set_btn_ctrl_all`.
+ *
  * @param btnm Button matrix object
  * @param one_toggle Whether "one toggle" mode is enabled
  */