diff --git a/.gitignore b/.gitignore
index a53ce7fd0..4a780c305 100644
--- a/.gitignore
+++ b/.gitignore
@@ -84,6 +84,7 @@ target
 *.gcov
 *.gcda
 *.gcno
+*.ubj
 build_tests
 /tests/cpp/xgboost_test