https://github.com/Blosc/c-blosc/issues/316
diff --git a/c-blosc/internal-complibs/zlib-1.2.8/gzguts.h b/c-blosc/internal-complibs/zlib-1.2.8/gzguts.h
index d87659d..f6823ed 100644
--- a/c-blosc/internal-complibs/zlib-1.2.8/gzguts.h
+++ b/c-blosc/internal-complibs/zlib-1.2.8/gzguts.h
@@ -26,6 +26,7 @@
 #  include <limits.h>
 #endif
 #include <fcntl.h>
+#include <unistd.h>

 #ifdef _WIN32
 #  include <stddef.h>