GPR_ASSERT is not an expression
diff --git a/build.json b/build.json
index 39e61d2..18591d6 100644
--- a/build.json
+++ b/build.json
@@ -370,7 +370,8 @@
         "src/core/support/thd_win32.c",
         "src/core/support/time.c",
         "src/core/support/time_posix.c",
-        "src/core/support/time_win32.c"
+        "src/core/support/time_win32.c",
+        "src/core/support/tls_pthread.c"
       ],
       "secure": "no",
       "vs_project_guid": "{B23D3D1A-9438-4EDA-BEB6-9A0A03D17792}"