diff --git a/tests/time_test.cpp b/tests/time_test.cpp
index 02163a5..fb5a4a7 100644
--- a/tests/time_test.cpp
+++ b/tests/time_test.cpp
@@ -55,7 +55,7 @@
   ASSERT_EQ(1970, broken_down->tm_year + 1900);
 }
 
-#ifdef __BIONIC__
+#if __BIONIC__
 TEST(time, mktime_10310929) {
   struct tm t;
   memset(&t, 0, sizeof(tm));
@@ -63,7 +63,23 @@
   t.tm_mon = 2;
   t.tm_mday = 10;
 
+#if !defined(__LP64__)
+  // 32-bit bionic stupidly had a signed 32-bit time_t.
   ASSERT_EQ(-1, mktime(&t));
   ASSERT_EQ(-1, mktime_tz(&t, "UTC"));
+#else
+  // Everyone else should be using a signed 64-bit time_t.
+  ASSERT_GE(sizeof(time_t) * 8, 64U);
+
+  setenv("TZ", "America/Los_Angeles", 1);
+  tzset();
+  ASSERT_EQ(static_cast<time_t>(4108348800U), mktime(&t));
+  ASSERT_EQ(static_cast<time_t>(4108320000U), mktime_tz(&t, "UTC"));
+
+  setenv("TZ", "UTC", 1);
+  tzset();
+  ASSERT_EQ(static_cast<time_t>(4108320000U), mktime(&t));
+  ASSERT_EQ(static_cast<time_t>(4108348800U), mktime_tz(&t, "America/Los_Angeles"));
+#endif
 }
 #endif