diff --git a/src/Lean/Compiler/LCNF/ToLCNF.lean b/src/Lean/Compiler/LCNF/ToLCNF.lean
index 84f78e080a..cd13425a9c 100644
--- a/src/Lean/Compiler/LCNF/ToLCNF.lean
+++ b/src/Lean/Compiler/LCNF/ToLCNF.lean
@@ -714,7 +714,7 @@ where
       return .fvar funDecl.fvarId
 
   visitMData (mdata : MData) (e : Expr) : M Expr := do
-    if let some (.app (.lam n t b ..) v) := letFunAnnotation? e then
+    if let some (.app (.lam n t b ..) v) := letFunAnnotation? (.mdata mdata e) then
       visitLet (.letE n t v b (nonDep := true)) #[]
     else if isCompilerRelevantMData mdata then
       mkAuxLetDecl <| .mdata mdata (← visit e)