diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index daf679a5a..fa379d577 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3859,6 +3859,9 @@ void EvalState::createBaseEnv()
     v.mkInt(6);
     addConstant("__langVersion", v);
 
+    v.mkBool(true);
+    addConstant("__super", v);
+
     // Miscellaneous
     if (evalSettings.enableNativeCode) {
         addPrimOp("__importNative", 2, prim_importNative);