diff --git a/Export.lean b/Export.lean
index 7a73832..12459e1 100644
--- a/Export.lean
+++ b/Export.lean
@@ -78,7 +78,7 @@ def removeMData (e : Expr) : M Expr := do
   | .lam _ d b _ =>
     pure <| e.updateLambdaE! (← removeMData d) (← removeMData b)
   | .letE _ d v b _ =>
-    pure <| e.updateLet! (← removeMData d) (← removeMData v) (← removeMData b)
+    pure <| e.updateLet! (← removeMData d) (← removeMData v) (← removeMData b) false
   | .forallE _ d b _ =>
     pure <| e.updateForallE! (← removeMData d) (← removeMData b)
   | .proj _ _ e2 =>
diff --git a/lean-toolchain b/lean-toolchain
index 1efd365..fff0a20 100644
--- a/lean-toolchain
+++ b/lean-toolchain
@@ -1 +1 @@
-leanprover/lean4:v4.21.0-rc3
+leanprover/lean4:v4.22.0-rc3