diff --git a/gzguts.h b/gzguts.h
index e23f831..f937504 100644
--- a/gzguts.h
+++ b/gzguts.h
@@ -7,9 +7,8 @@
 #  ifndef _LARGEFILE_SOURCE
 #    define _LARGEFILE_SOURCE 1
 #  endif
-#  ifdef _FILE_OFFSET_BITS
-#    undef _FILE_OFFSET_BITS
-#  endif
+#  undef _FILE_OFFSET_BITS
+#  undef _TIME_BITS
 #endif
 
 #ifdef HAVE_HIDDEN