diff --git a/lib/gollum/wiki.rb b/lib/gollum/wiki.rb
index 8f042c5b..ea9bddd6 100644
--- a/lib/gollum/wiki.rb
+++ b/lib/gollum/wiki.rb
@@ -520,11 +520,14 @@ module Gollum
     #
     # Returns a flat Array of Gollum::Page instances.
     def tree_list(ref)
-      sha    = @access.ref_to_sha(ref)
-      commit = @access.commit(sha)
-      tree_map_for(sha).inject([]) do |list, entry|
-        next list unless @page_class.valid_page_name?(entry.name)
-        list << entry.page(self, commit)
+      if sha = @access.ref_to_sha(ref)
+        commit = @access.commit(sha)
+        tree_map_for(sha).inject([]) do |list, entry|
+          next list unless @page_class.valid_page_name?(entry.name)
+          list << entry.page(self, commit)
+        end
+      else
+        []
       end
     end