diff --git a/ha_mroonga.cpp b/ha_mroonga.cpp
index 822989258..7e6c250cf 100644
--- a/ha_mroonga.cpp
+++ b/ha_mroonga.cpp
@@ -557,7 +557,7 @@ static void mrn_logger_func(int level, const char *time, const char *title,
     pthread_mutex_lock(&mrn_log_mutex);
     fprintf(mrn_log_file, "%s|%c|%08x|%s\n", time,
             *(slev + level),
-            static_cast<uint>(static_cast<ulong>(pthread_self())),
+            static_cast<uint>((ulong)(pthread_self())),
             msg);
     fflush(mrn_log_file);
     pthread_mutex_unlock(&mrn_log_mutex);