diff --git a/deps/zlib/zlib.gyp b/deps/zlib/zlib.gyp
index fac801c7cbf362..fad1c94c1691ad 100644
--- a/deps/zlib/zlib.gyp
+++ b/deps/zlib/zlib.gyp
@@ -62,6 +62,7 @@
             ['OS!="win"', {
               'product_name': 'chrome_zlib',
               'cflags!': [ '-ansi' ],
+              'defines': [ 'Z_HAVE_UNISTD_H' ],
               'sources!': [
                 'contrib/minizip/iowin32.c'
               ],