diff --git a/capnp/fixMaybe.h b/capnp/fixMaybe.h
index be56680..a1dfac6 100644
--- a/capnp/fixMaybe.h
+++ b/capnp/fixMaybe.h
@@ -1,6 +1,8 @@
 #include "kj/common.h"
 #include <stdexcept>
 
+static_assert(CAPNP_VERSION >= 3000, "Version of Cap'n Proto C++ Library is too old. Please upgrade to a version >= 0.3 and then re-install this python library");
+
 template<typename T>
 T fixMaybe(::kj::Maybe<T> val) {
   KJ_IF_MAYBE(new_val, val) {