diff --git a/lib/fpurge.c b/lib/fpurge.c
index b1d417c7a..75cf34ca2 100644
--- a/lib/fpurge.c
+++ b/lib/fpurge.c
@@ -62,7 +62,7 @@ fpurge (FILE *fp)
   /* Most systems provide FILE as a struct and the necessary bitmask in
      <stdio.h>, because they need it for implementing getc() and putc() as
      fast macros.  */
-# if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+# if defined _IO_ftrylockfile || __GNU_LIBRARY__ /* GNU libc, BeOS, Haiku, Linux libc5 */
   fp->_IO_read_end = fp->_IO_read_ptr;
   fp->_IO_write_ptr = fp->_IO_write_base;
   /* Avoid memory leak when there is an active ungetc buffer.  */