diff --git a/flang/lib/Optimizer/CodeGen/BoxedProcedure.cpp b/flang/lib/Optimizer/CodeGen/BoxedProcedure.cpp
index 846a78931acba..4cf39716a7375 100644
--- a/flang/lib/Optimizer/CodeGen/BoxedProcedure.cpp
+++ b/flang/lib/Optimizer/CodeGen/BoxedProcedure.cpp
@@ -342,7 +342,7 @@ class BoxedProcedurePass
             auto toTy = typeConverter.convertType(ty);
             auto toOnTy = typeConverter.convertType(onTy);
             rewriter.replaceOpWithNewOp<LenParamIndexOp>(
-                mem, toTy, index.getFieldId(), toOnTy, index.getTypeparams());
+                index, toTy, index.getFieldId(), toOnTy, index.getTypeparams());
           }
         } else if (op->getDialect() == firDialect) {
           rewriter.startOpModification(op);