diff --git a/libwccl/ops/actionexeccontext.h b/libwccl/ops/actionexeccontext.h
index 27115e566f494e648b86f7e4aab7fcd1508a504a..b49b5134115733d431c4dbad47e1dcc52b901e9f 100644
--- a/libwccl/ops/actionexeccontext.h
+++ b/libwccl/ops/actionexeccontext.h
@@ -18,6 +18,7 @@ public:
 			const boost::shared_ptr<Variables>& vars)
 		: sentence_context_(sentence_context), vars_(vars)
 	{
+		BOOST_ASSERT(vars_);
 	}
 
 	/**