diff --git a/gtk/gtktoolbar.c b/gtk/gtktoolbar.c
index f5d7fb298b..ecc7832d16 100644
--- a/gtk/gtktoolbar.c
+++ b/gtk/gtktoolbar.c
@@ -631,13 +631,21 @@ gtk_toolbar_class_init (GtkToolbarClass *klass)
                                                              G_MAXINT,
                                                              GTK_PARAM_READABLE));
 
+  /**
+   * GtkToolbar:space-style:
+   *
+   * Style of toolbar spacers.
+   *
+   * Deprecated: 3.20: Use CSS properties on the separator elements to style
+   *   toolbar spacers; the value of this style property is ignored.
+   */
   gtk_widget_class_install_style_property (widget_class,
 					   g_param_spec_enum ("space-style",
 							      P_("Space style"),
 							      P_("Whether spacers are vertical lines or just blank"),
                                                               GTK_TYPE_TOOLBAR_SPACE_STYLE,
                                                               DEFAULT_SPACE_STYLE,
-                                                              GTK_PARAM_READABLE));
+                                                              GTK_PARAM_READABLE|G_PARAM_DEPRECATED));
   
   gtk_widget_class_install_style_property (widget_class,
 					   g_param_spec_enum ("button-relief",
diff --git a/gtk/gtktoolbar.h b/gtk/gtktoolbar.h
index f91ecfbb4f..9937579297 100644
--- a/gtk/gtktoolbar.h
+++ b/gtk/gtktoolbar.h
@@ -54,6 +54,8 @@ G_BEGIN_DECLS
  * @GTK_TOOLBAR_SPACE_LINE: Use vertical lines for spacers.
  *
  * Whether spacers are vertical lines or just blank.
+ *
+ * Deprecated: 3.20
  */
 typedef enum
 {