diff --git a/glib/gdataset.c b/glib/gdataset.c
index b29042c54..66b50e22e 100644
--- a/glib/gdataset.c
+++ b/glib/gdataset.c
@@ -1371,12 +1371,12 @@ g_datalist_id_replace_data (GData          **datalist,
             }
         }
     }
-
-  if (val == NULL && oldval == NULL && newval != NULL)
+  else
     {
-      if (datalist_append (&d, key_id, newval, destroy))
+      if (oldval == NULL && newval != NULL)
         {
-          set_d = TRUE;
+          if (datalist_append (&d, key_id, newval, destroy))
+            set_d = TRUE;
         }
     }