Fix include guards
diff --git a/src/core/lib/support/time_precise.h b/src/core/lib/support/time_precise.h
index 871c99a..e1faee1 100644
--- a/src/core/lib/support/time_precise.h
+++ b/src/core/lib/support/time_precise.h
@@ -31,12 +31,12 @@
  *
  */
 
-#ifndef GRPC_CORE_SUPPORT_TIME_PRECISE_H
-#define GRPC_CORE_SUPPORT_TIME_PRECISE_H
+#ifndef GRPC_CORE_LIB_SUPPORT_TIME_PRECISE_H
+#define GRPC_CORE_LIB_SUPPORT_TIME_PRECISE_H
 
 #include <grpc/support/time.h>
 
 void gpr_precise_clock_init(void);
 void gpr_precise_clock_now(gpr_timespec *clk);
 
-#endif /* GRPC_CORE_SUPPORT_TIME_PRECISE_H */
+#endif /* GRPC_CORE_LIB_SUPPORT_TIME_PRECISE_H */