diff --git a/libio/ChangeLog b/libio/ChangeLog
index aa546a46c4c..4bcc68412de 100644
--- a/libio/ChangeLog
+++ b/libio/ChangeLog
@@ -1,3 +1,7 @@
+1999-05-17  Mark Kettenis  <kettenis@gnu.org>
+
+	* libioP.h: Only include libc-lock.h if _IO_MTSAFE_IO is defined.
+
 1999-05-12  Jason Merrill  <jason@yorick.cygnus.com>
 
 	* configure.in (compiler_name): Don't do the skip-this-dir thing
diff --git a/libio/libioP.h b/libio/libioP.h
index 36fa1e007de..629e4fd8cf6 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -31,14 +31,17 @@
 #ifndef __set_errno
 # define __set_errno(Val) errno = (Val)
 #endif
-#if defined __GLIBC__ && __GLIBC__ >= 2
-# if __GLIBC_MINOR__ > 0
-#  include <bits/libc-lock.h>
+
+#ifdef _IO_MTSAFE_IO
+# if defined __GLIBC__ && __GLIBC__ >= 2
+#  if __GLIBC_MINOR__ > 0
+#   include <bits/libc-lock.h>
+#  else
+#   include <libc-lock.h>
+#  endif
 # else
-#  include <libc-lock.h>
-# endif
-#else
 /*# include <comthread.h>*/
+# endif
 #endif
 
 #include "iolibio.h"