--- a/wscript
+++ b/wscript
@@ -191,7 +191,7 @@
 
     conf.CHECK_CFG(package='zlib', minversion='1.2.3',
                    args='--cflags --libs',
-                   mandatory=True)
+                   mandatory=False)
     conf.CHECK_FUNCS_IN('inflateInit2', 'z')
 
     if conf.CHECK_FOR_THIRD_PARTY():