diff --git a/tile/base/thread/cond_var_test.cc b/tile/base/thread/cond_var_test.cc
index b489c58..033182c 100644
--- a/tile/base/thread/cond_var_test.cc
+++ b/tile/base/thread/cond_var_test.cc
@@ -30,8 +30,8 @@ class CondVarTest : public ::testing::Test {
 protected:
   Mutex *m;
   CondVar *cv;
-  bool is_set;
-  bool is_timeout;
+  volatile bool is_set;
+  volatile bool is_timeout;
   std::thread *worker;
 };