diff --git a/gtk/gtkcssanimation.c b/gtk/gtkcssanimation.c
index 48ef62bc49..e4c692a19c 100644
--- a/gtk/gtkcssanimation.c
+++ b/gtk/gtkcssanimation.c
@@ -97,9 +97,8 @@ gtk_css_animation_get_progress_from_iteration (GtkCssAnimation *animation,
     }
 }
 
-static GtkBitmask *
+static void
 gtk_css_animation_set_values (GtkStyleAnimation    *style_animation,
-                              GtkBitmask           *changed,
                               gint64                for_time_us,
                               GtkCssComputedValues *values)
 {
@@ -110,7 +109,7 @@ gtk_css_animation_set_values (GtkStyleAnimation    *style_animation,
   iteration = gtk_css_animation_get_iteration (animation, for_time_us);
 
   if (!gtk_css_animation_is_executing_at_iteration (animation, iteration))
-    return changed;
+    return;
 
   progress = gtk_css_animation_get_progress_from_iteration (animation, iteration);
   progress = _gtk_css_ease_value_transform (animation->ease, progress);
@@ -128,11 +127,7 @@ gtk_css_animation_set_values (GtkStyleAnimation    *style_animation,
                                             _gtk_css_computed_values_get_intrinsic_value (values, i));
       _gtk_css_computed_values_set_animated_value (values, property_id, value);
       _gtk_css_value_unref (value);
-      
-      changed = _gtk_bitmask_set (changed, property_id, TRUE);
     }
-
-  return changed;
 }
 
 static gboolean
diff --git a/gtk/gtkcsscomputedvalues.c b/gtk/gtkcsscomputedvalues.c
index 98d827da9f..283412404d 100644
--- a/gtk/gtkcsscomputedvalues.c
+++ b/gtk/gtkcsscomputedvalues.c
@@ -513,8 +513,6 @@ _gtk_css_computed_values_advance (GtkCssComputedValues *values,
   g_return_val_if_fail (GTK_IS_CSS_COMPUTED_VALUES (values), NULL);
   g_return_val_if_fail (timestamp >= values->current_time, NULL);
 
-  changed = _gtk_bitmask_new ();
-
   values->current_time = timestamp;
   old_computed_values = values->animated_values;
   values->animated_values = NULL;
@@ -526,10 +524,9 @@ _gtk_css_computed_values_advance (GtkCssComputedValues *values,
       
       list = list->next;
 
-      changed = _gtk_style_animation_set_values (animation,
-                                                 changed,
-                                                 timestamp,
-                                                 GTK_CSS_COMPUTED_VALUES (values));
+      _gtk_style_animation_set_values (animation,
+                                       timestamp,
+                                       GTK_CSS_COMPUTED_VALUES (values));
       
       if (_gtk_style_animation_is_finished (animation, timestamp))
         {
@@ -538,8 +535,6 @@ _gtk_css_computed_values_advance (GtkCssComputedValues *values,
         }
     }
 
-  _gtk_bitmask_free (changed);
-  
   /* figure out changes */
   changed = _gtk_bitmask_new ();
 
diff --git a/gtk/gtkcsstransition.c b/gtk/gtkcsstransition.c
index bc50e66c77..8aa7737a2f 100644
--- a/gtk/gtkcsstransition.c
+++ b/gtk/gtkcsstransition.c
@@ -25,9 +25,8 @@
 
 G_DEFINE_TYPE (GtkCssTransition, _gtk_css_transition, GTK_TYPE_STYLE_ANIMATION)
 
-static GtkBitmask *
+static void
 gtk_css_transition_set_values (GtkStyleAnimation    *animation,
-                               GtkBitmask           *changed,
                                gint64                for_time_us,
                                GtkCssComputedValues *values)
 {
@@ -54,8 +53,6 @@ gtk_css_transition_set_values (GtkStyleAnimation    *animation,
 
   _gtk_css_computed_values_set_animated_value (values, transition->property, value);
   _gtk_css_value_unref (value);
-
-  return _gtk_bitmask_set (changed, transition->property, TRUE);
 }
 
 static gboolean
diff --git a/gtk/gtkstyleanimation.c b/gtk/gtkstyleanimation.c
index ac74851c59..2ee49f3fa8 100644
--- a/gtk/gtkstyleanimation.c
+++ b/gtk/gtkstyleanimation.c
@@ -23,13 +23,11 @@
 
 G_DEFINE_ABSTRACT_TYPE (GtkStyleAnimation, _gtk_style_animation, G_TYPE_OBJECT)
 
-static GtkBitmask *
+static void
 gtk_style_animation_real_set_values (GtkStyleAnimation    *animation,
-                                     GtkBitmask           *changed,
                                      gint64                for_time_us,
                                      GtkCssComputedValues *values)
 {
-  return changed;
 }
 
 static gboolean
@@ -59,20 +57,19 @@ _gtk_style_animation_init (GtkStyleAnimation *animation)
 {
 }
 
-GtkBitmask *
+void
 _gtk_style_animation_set_values (GtkStyleAnimation    *animation,
-                                 GtkBitmask           *changed,
                                  gint64                for_time_us,
                                  GtkCssComputedValues *values)
 {
   GtkStyleAnimationClass *klass;
 
-  g_return_val_if_fail (GTK_IS_STYLE_ANIMATION (animation), changed);
-  g_return_val_if_fail (GTK_IS_CSS_COMPUTED_VALUES (values), changed);
+  g_return_if_fail (GTK_IS_STYLE_ANIMATION (animation));
+  g_return_if_fail (GTK_IS_CSS_COMPUTED_VALUES (values));
 
   klass = GTK_STYLE_ANIMATION_GET_CLASS (animation);
 
-  return klass->set_values (animation, changed, for_time_us, values);
+  return klass->set_values (animation, for_time_us, values);
 }
 
 gboolean
diff --git a/gtk/gtkstyleanimationprivate.h b/gtk/gtkstyleanimationprivate.h
index b4f2c69595..4db2a0792e 100644
--- a/gtk/gtkstyleanimationprivate.h
+++ b/gtk/gtkstyleanimationprivate.h
@@ -48,18 +48,16 @@ struct _GtkStyleAnimationClass
                                                          gint64                  at_time_us);
   gboolean      (* is_static)                           (GtkStyleAnimation      *animation,
                                                          gint64                  at_time_us);
-  GtkBitmask *  (* set_values)                          (GtkStyleAnimation      *animation,
-                                                         GtkBitmask             *changed,
+  void          (* set_values)                          (GtkStyleAnimation      *animation,
                                                          gint64                  for_time_us,
                                                          GtkCssComputedValues   *values);
 };
 
 GType           _gtk_style_animation_get_type           (void) G_GNUC_CONST;
 
-GtkBitmask *    _gtk_style_animation_set_values         (GtkStyleAnimation      *animation,
-                                                         GtkBitmask             *changed,
+void            _gtk_style_animation_set_values         (GtkStyleAnimation      *animation,
                                                          gint64                  for_time_us,
-                                                         GtkCssComputedValues   *values) G_GNUC_WARN_UNUSED_RESULT;
+                                                         GtkCssComputedValues   *values);
 gboolean        _gtk_style_animation_is_finished        (GtkStyleAnimation      *animation,
                                                          gint64                  at_time_us);
 gboolean        _gtk_style_animation_is_static          (GtkStyleAnimation      *animation,