diff --git a/gio/gcontenttype.c b/gio/gcontenttype.c
index d54f04202..8734e7f4b 100644
--- a/gio/gcontenttype.c
+++ b/gio/gcontenttype.c
@@ -1032,11 +1032,16 @@ read_tree_magic_from_directory (const gchar *prefix)
                   match = parse_header (lines[i]);
                   insert_match (match);
                 }
-              else
+              else if (match != NULL)
                 {
                   matchlet = parse_match_line (lines[i], &depth);
                   insert_matchlet (match, matchlet, depth);
                 }
+              else
+                {
+                  g_warning ("%s: header corrupt; skipping\n", filename);
+                  break;
+                }
             }
 
           g_strfreev (lines);