diff --git a/acx_nlnetlabs.m4 b/acx_nlnetlabs.m4
index bc18187fd..e393817ef 100644
--- a/acx_nlnetlabs.m4
+++ b/acx_nlnetlabs.m4
@@ -2,7 +2,8 @@
 # Copyright 2009, Wouter Wijngaards, NLnet Labs.   
 # BSD licensed.
 #
-# Version 22
+# Version 23
+# 2013-05-03 Update W32_SLEEP for newer mingw that links but not defines it.
 # 2013-03-22 Fix ACX_RSRC_VERSION for long version numbers.
 # 2012-02-09 Fix AHX_MEMCMP_BROKEN with undef in compat/memcmp.h.
 # 2012-01-20 Fix COMPILER_FLAGS_UNBOUND for gcc 4.6.2 assigned-not-used-warns.
@@ -1209,7 +1210,7 @@ struct tm *gmtime_r(const time_t *timep, struct tm *result);
 dnl provide w32 compat definition for sleep
 AC_DEFUN([AHX_CONFIG_W32_SLEEP],
 [
-#ifndef HAVE_SLEEP
+#if !defined(HAVE_SLEEP) || defined(HAVE_WINDOWS_H)
 #define sleep(x) Sleep((x)*1000) /* on win32 */
 #endif /* HAVE_SLEEP */
 ])
diff --git a/config.h.in b/config.h.in
index 7e1a5a34b..eb1f27053 100644
--- a/config.h.in
+++ b/config.h.in
@@ -805,7 +805,7 @@ struct tm *gmtime_r(const time_t *timep, struct tm *result);
 #endif
 
 
-#ifndef HAVE_SLEEP
+#if !defined(HAVE_SLEEP) || defined(HAVE_WINDOWS_H)
 #define sleep(x) Sleep((x)*1000) /* on win32 */
 #endif /* HAVE_SLEEP */
 
diff --git a/doc/Changelog b/doc/Changelog
index 2b0b80aa0..88eac6c7c 100644
--- a/doc/Changelog
+++ b/doc/Changelog
@@ -1,3 +1,6 @@
+3 May 2013: Wouter
+	- update acx_nlnetlabs.m4 to v23, sleep w32 fix.
+
 26 April 2013: Wouter
 	- add unbound-control insecure_add and insecure_remove for the
 	  administration of negative trust anchors.