diff --git a/src/st/st-theme-node.c b/src/st/st-theme-node.c
index 1b8b4d0b2..cf6769ac9 100644
--- a/src/st/st-theme-node.c
+++ b/src/st/st-theme-node.c
@@ -204,7 +204,7 @@ st_theme_node_get_pseudo_class (StThemeNode *node)
   return node->pseudo_class;
 }
 
-void
+static void
 ensure_properties (StThemeNode *node)
 {
   if (!node->properties_computed)