diff --git a/gtk/gtkradiobutton.c b/gtk/gtkradiobutton.c
index e22adf68a7..ff607cea56 100644
--- a/gtk/gtkradiobutton.c
+++ b/gtk/gtkradiobutton.c
@@ -403,7 +403,8 @@ gtk_radio_button_join_group (GtkRadioButton *radio_button,
 
 /**
  * gtk_radio_button_new:
- * @group: an existing radio button group, or %NULL if you are creating a new group.
+ * @group: (allow-none): an existing radio button group, or %NULL if you are
+ *  creating a new group.
  *
  * Creates a new #GtkRadioButton. To be of any practical value, a widget should
  * then be packed into the radio button.
@@ -425,8 +426,8 @@ gtk_radio_button_new (GSList *group)
 
 /**
  * gtk_radio_button_new_with_label:
- * @group: an existing radio button group, or %NULL if you are creating a new
- *  group.
+ * @group: (allow-none): an existing radio button group, or %NULL if you are
+ *  creating a new group.
  * @label: the text label to display next to the radio button.
  *
  * Creates a new #GtkRadioButton with a text label.
@@ -450,7 +451,7 @@ gtk_radio_button_new_with_label (GSList      *group,
 
 /**
  * gtk_radio_button_new_with_mnemonic:
- * @group: the radio button group
+ * @group: (allow-none): the radio button group
  * @label: the text of the button, with an underscore in front of the
  *         mnemonic character
  *
@@ -480,7 +481,7 @@ gtk_radio_button_new_with_mnemonic (GSList      *group,
 
 /**
  * gtk_radio_button_new_from_widget:
- * @radio_group_member: an existing #GtkRadioButton.
+ * @radio_group_member: (allow-none): an existing #GtkRadioButton.
  *
  * Creates a new #GtkRadioButton, adding it to the same group as
  * @radio_group_member. As with gtk_radio_button_new(), a widget
@@ -499,7 +500,7 @@ gtk_radio_button_new_from_widget (GtkRadioButton *radio_group_member)
 
 /**
  * gtk_radio_button_new_with_label_from_widget:
- * @radio_group_member: widget to get radio group from or %NULL
+ * @radio_group_member: (allow-none): widget to get radio group from or %NULL
  * @label: a text string to display next to the radio button.
  *
  * Creates a new #GtkRadioButton with a text label, adding it to