diff --git a/lib/rugged/commit.rb b/lib/rugged/commit.rb
index <HASH>..<HASH> 100644
--- a/lib/rugged/commit.rb
+++ b/lib/rugged/commit.rb
@@ -6,7 +6,7 @@ module Rugged
     end
 
     def inspect
-      "#<Rugged::Commit:#{object_id} {message: #{message.inspect}, tree: #{tree.inspect}, parents: #{parent_ids}>"
+      "#<Rugged::Commit:#{object_id} {message: #{message.inspect}, tree: #{tree.inspect}, parents: #{parent_oids}>"
     end
 
     # The time when this commit was made effective. This is the same value
@@ -26,10 +26,6 @@ module Rugged
         :parents => parents,
       }
     end
-    
-    def parent_ids
-      parents.map { |parent| parent.oid }
-    end
 
     def modify(new_args, update_ref=nil)
       args = self.to_hash.merge(new_args)
Remove useless method: "parent_ids"

Use "parent_oids" in ext instead of "parent_ids"