diff --git a/tests/unit/rangeset_test.cpp b/tests/unit/rangeset_test.cpp
index 7ae193e..fc72f2f 100644
--- a/tests/unit/rangeset_test.cpp
+++ b/tests/unit/rangeset_test.cpp
@@ -209,6 +209,7 @@
   ASSERT_EQ(static_cast<size_t>(6), rs.GetBlockNumber(5));
   ASSERT_EQ(static_cast<size_t>(9), rs.GetBlockNumber(8));
 
+  ::testing::FLAGS_gtest_death_test_style = "threadsafe";
   // Out of bound.
   ASSERT_EXIT(rs.GetBlockNumber(9), ::testing::KilledBySignal(SIGABRT), "");
 }
@@ -284,6 +285,8 @@
 
   ASSERT_EQ(static_cast<size_t>(10), rs.GetOffsetInRangeSet(4106));
   ASSERT_EQ(static_cast<size_t>(40970), rs.GetOffsetInRangeSet(4096 * 16 + 10));
+
+  ::testing::FLAGS_gtest_death_test_style = "threadsafe";
   // block#10 not in range.
   ASSERT_EXIT(rs.GetOffsetInRangeSet(40970), ::testing::KilledBySignal(SIGABRT), "");
 }
diff --git a/tests/unit/screen_ui_test.cpp b/tests/unit/screen_ui_test.cpp
index 2562307..2179b72 100644
--- a/tests/unit/screen_ui_test.cpp
+++ b/tests/unit/screen_ui_test.cpp
@@ -408,5 +408,7 @@
   ASSERT_TRUE(ui_->Init(kTestLocale));
   TemporaryDir resource_dir;
   Paths::Get().set_resource_dir(resource_dir.path);
+
+  ::testing::FLAGS_gtest_death_test_style = "threadsafe";
   ASSERT_EXIT(ui_->RunLoadAnimation(), ::testing::KilledBySignal(SIGABRT), "");
 }