diff --git a/gtk/inspector/visual.c b/gtk/inspector/visual.c
index 7fcf969905..8136fc3396 100644
--- a/gtk/inspector/visual.c
+++ b/gtk/inspector/visual.c
@@ -1049,6 +1049,7 @@ update_gl_flag (GtkSwitch     *sw,
 
 static void
 software_gl_activate (GtkSwitch *sw,
+                      GParamSpec *pspec,
                       GtkInspectorVisual *vis)
 {
   update_gl_flag (sw, GDK_DEBUG_GL_SOFTWARE, vis);