diff --git a/src/engine/engine.cc b/src/engine/engine.cc
index d79289ec2..218f08fe9 100644
--- a/src/engine/engine.cc
+++ b/src/engine/engine.cc
@@ -51,7 +51,6 @@
 #include "dictionary/user_dictionary.h"
 #include "dictionary/user_pos.h"
 #include "engine/user_data_manager_interface.h"
-#include "ngram/neg_log_prob.h"
 #include "prediction/dictionary_predictor.h"
 #include "prediction/predictor.h"
 #include "prediction/predictor_interface.h"