diff --git a/lily/scale.cc b/lily/scale.cc
index e3fe7ba..a14d8b3 100644
--- a/lily/scale.cc
+++ b/lily/scale.cc
@@ -89,9 +89,11 @@ LY_DEFINE (ly_set_default_scale, "ly:set-default-scale",
 
   Scale *s = Scale::unsmob (scale);
   if (default_global_scale)
-    default_global_scale->unprotect ();
-  default_global_scale = s;
-  s->protect ();
+    *default_global_scale = *s;
+  else {
+    default_global_scale = s;
+    s->protect ();
+  }
   
   return SCM_UNSPECIFIED;
 }