diff --git a/cc/config/clang.go b/cc/config/clang.go
index 71bea4263..1b6744e61 100644
--- a/cc/config/clang.go
+++ b/cc/config/clang.go
@@ -139,9 +139,7 @@ func init() {
 
 	pctx.StaticVariable("ClangExtraCppflags", strings.Join([]string{
 		// Enable clang's thread-safety annotations in libcxx.
-		// Turn off -Wthread-safety-negative, to avoid breaking projects that use -Weverything.
 		"-D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS",
-		"-Wno-thread-safety-negative",
 
 		// libc++'s math.h has an #include_next outside of system_headers.
 		"-Wno-gnu-include-next",