diff --git a/gtk/inspector/size-groups.c b/gtk/inspector/size-groups.c
index eb185ed..f7c604d 100644
--- a/gtk/inspector/size-groups.c
+++ b/gtk/inspector/size-groups.c
@@ -44,7 +44,7 @@ enum {
   LAST_PROPERTY
 };
 
-GParamSpec *properties[LAST_PROPERTY] = { NULL };
+static GParamSpec *properties[LAST_PROPERTY] = { NULL };
 
 GType size_group_row_get_type (void);