diff --git a/wscript b/wscript
index 42532e7..836558e 100644
--- a/wscript
+++ b/wscript
@@ -44,6 +44,8 @@
     conf.env['WITH_TESTS'] = conf.options.with_tests
     conf.env['WITH_TOOLS'] = conf.options.with_tools
 
+    conf.find_program('sh', var='SH', mandatory=True)
+
     conf.check_osx_security(mandatory=False)
 
     conf.check_openssl(mandatory=True)