diff --git a/RELEASE_NOTES.rst b/RELEASE_NOTES.rst
index 0a88a8cd..810f2c04 100644
--- a/RELEASE_NOTES.rst
+++ b/RELEASE_NOTES.rst
@@ -5,8 +5,10 @@
 Changes from 1.21.0 to 1.21.1
 =============================
 
-#XXX version-specific blurb XXX#
 
+* BloscLZ updated to 2.5.1
+* Zlib updated to 1.2.11
+* Zstd updated to 1.5.0
 
 Changes from 1.20.1 to 1.21.0
 =============================
diff --git a/internal-complibs/zlib-1.2.11/gzguts.h b/internal-complibs/zlib-1.2.11/gzguts.h
index d7e74769..45be5735 100644
--- a/internal-complibs/zlib-1.2.11/gzguts.h
+++ b/internal-complibs/zlib-1.2.11/gzguts.h
@@ -3,7 +3,9 @@
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
-#include <unistd.h>
+#ifndef _WIN32
+#  include <unistd.h>
+#endif
 
 #ifdef _LARGEFILE64_SOURCE
 #  ifndef _LARGEFILE_SOURCE