diff --git a/src/st/st-theme-node-drawing.c b/src/st/st-theme-node-drawing.c
index 8e5814184..c3424f9fd 100644
--- a/src/st/st-theme-node-drawing.c
+++ b/src/st/st-theme-node-drawing.c
@@ -2088,3 +2088,10 @@ st_theme_node_copy_cached_paint_state (StThemeNode *node,
     if (other->corner_material[corner_id])
       node->corner_material[corner_id] = cogl_handle_ref (other->corner_material[corner_id]);
 }
+
+void
+st_theme_node_invalidate_paint_state (StThemeNode *node)
+{
+  node->alloc_width = 0;
+  node->alloc_height = 0;
+}
diff --git a/src/st/st-theme-node.h b/src/st/st-theme-node.h
index 795f875c1..2c672ebcf 100644
--- a/src/st/st-theme-node.h
+++ b/src/st/st-theme-node.h
@@ -244,6 +244,7 @@ void st_theme_node_paint (StThemeNode            *node,
 
 void st_theme_node_copy_cached_paint_state (StThemeNode *node,
                                             StThemeNode *other);
+void st_theme_node_invalidate_paint_state  (StThemeNode *node);
 
 G_END_DECLS