diff --git a/old/trainer.cpp b/zinnia-0.06/trainer.cpp
index fdb044c..8b21e6c 100644
--- a/old/trainer.cpp
+++ b/zinnia-0.06/trainer.cpp
@@ -103,7 +103,7 @@ class TrainerImpl: public Trainer {
     if (!fn) {
       return false;
     }
-    x_.push_back(std::make_pair<std::string, FeatureNode *>(y, fn));
+    x_.push_back(std::make_pair(y, fn));
     return true;
   }