diff --git a/flang/include/flang/Optimizer/Dialect/FIRType.h b/flang/include/flang/Optimizer/Dialect/FIRType.h
--- a/flang/include/flang/Optimizer/Dialect/FIRType.h
+++ b/flang/include/flang/Optimizer/Dialect/FIRType.h
@@ -280,12 +280,6 @@
 /// e.g. !fir.box<!fir.type<derived>>
 bool isBoxedRecordType(mlir::Type ty);
 
-/// Return true iff `ty` is a !fir.ref<!fir.box<T>> type.
-bool isRefBoxType(mlir::Type ty);
-
-/// Return true iff `ty` is !fir.box<none> type.
-bool isOpaqueDescType(mlir::Type ty);
-
 /// Return true iff `ty` is the type of an polymorphic entity or
 /// value.
 bool isPolymorphicType(mlir::Type ty);
diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -2718,7 +2718,7 @@
               // course base_addr might need to be updated.
               if (lhsType && lhsType->IsUnlimitedPolymorphic()) {
                 mlir::Value lhs = genExprMutableBox(loc, assign.lhs).getAddr();
-                mlir::Value rhs = genExprMutableBox(loc, assign.rhs).getAddr();
+                mlir::Value rhs = fir::getBase(genExprBox(loc, assign.rhs, stmtCtx));
                 Fortran::lower::genPointerAssociate(*builder, loc, lhs, rhs);
                 return;
               }
diff --git a/flang/lib/Optimizer/Dialect/FIROps.cpp b/flang/lib/Optimizer/Dialect/FIROps.cpp
--- a/flang/lib/Optimizer/Dialect/FIROps.cpp
+++ b/flang/lib/Optimizer/Dialect/FIROps.cpp
@@ -938,8 +938,7 @@
       (inType.isa<fir::BoxProcType>() && outType.isa<fir::BoxProcType>()) ||
       (fir::isa_complex(inType) && fir::isa_complex(outType)) ||
       (fir::isBoxedRecordType(inType) && fir::isPolymorphicType(outType)) ||
-      (fir::isPolymorphicType(inType) && fir::isPolymorphicType(outType)) ||
-      (fir::isRefBoxType(inType) && fir::isOpaqueDescType(outType)))
+      (fir::isPolymorphicType(inType) && fir::isPolymorphicType(outType)))
     return mlir::success();
   llvm::errs() << inType << " / " << outType << "\n";
   return emitOpError("invalid type conversion");
diff --git a/flang/lib/Optimizer/Dialect/FIRType.cpp b/flang/lib/Optimizer/Dialect/FIRType.cpp
--- a/flang/lib/Optimizer/Dialect/FIRType.cpp
+++ b/flang/lib/Optimizer/Dialect/FIRType.cpp
@@ -274,19 +274,6 @@
   return false;
 }
 
-bool isRefBoxType(mlir::Type ty) {
-  if (auto refTy = ty.dyn_cast<fir::ReferenceType>())
-    return refTy.getEleTy().isa<fir::BaseBoxType>();
-  return false;
-}
-
-bool isOpaqueDescType(mlir::Type ty) {
-  if (auto boxTy = ty.dyn_cast<fir::BoxType>())
-    if (boxTy.getEleTy().isa<mlir::NoneType>())
-      return true;
-  return false;
-}
-
 static bool isAssumedType(mlir::Type ty) {
   if (auto boxTy = ty.dyn_cast<fir::BoxType>()) {
     if (boxTy.getEleTy().isa<mlir::NoneType>())
diff --git a/flang/test/Lower/polymorphic.f90 b/flang/test/Lower/polymorphic.f90
--- a/flang/test/Lower/polymorphic.f90
+++ b/flang/test/Lower/polymorphic.f90
@@ -141,9 +141,11 @@
 ! CHECK: %[[P:.*]] = fir.alloca !fir.class<!fir.ptr<!fir.array<?xnone>>> {bindc_name = "p", uniq_name = "_QMpolymorphic_testFassociate_up_pointerEp"}
 ! CHECK: %[[FIELD_RP:.*]] = fir.field_index rp, !fir.type<_QMpolymorphic_testTr1{rp:!fir.box<!fir.ptr<!fir.array<?xf32>>>}>
 ! CHECK: %[[COORD_RP:.*]] = fir.coordinate_of %[[ARG0]], %[[FIELD_RP]] : (!fir.class<!fir.type<_QMpolymorphic_testTr1{rp:!fir.box<!fir.ptr<!fir.array<?xf32>>>}>>, !fir.field) -> !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>
+! CHECK: %[[LOAD_RP:.*]] = fir.load %[[COORD_RP]] : !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>
+! CHECK: %[[REBOX_RP:.*]] = fir.rebox %[[LOAD_RP]](%{{.*}}) : (!fir.box<!fir.ptr<!fir.array<?xf32>>>, !fir.shift<1>) -> !fir.box<!fir.array<?xf32>>
 ! CHECK: %[[CONV_P:.*]] = fir.convert %[[P]] : (!fir.ref<!fir.class<!fir.ptr<!fir.array<?xnone>>>>) -> !fir.ref<!fir.box<none>>
-! CHECK: %[[CONV_RP:.*]] = fir.convert %[[COORD_RP]] : (!fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>) -> !fir.box<none>
-! CHECK: %{{.*}} = fir.call @_FortranAPointerAssociate(%[[CONV_P]], %[[CONV_RP]]) {{.*}} : (!fir.ref<!fir.box<none>>, !fir.box<none>) -> none
+! CHECK: %[[RP_BOX_NONE:.*]] = fir.convert %[[REBOX_RP]] : (!fir.box<!fir.array<?xf32>>) -> !fir.box<none>
+! CHECK: %{{.*}} = fir.call @_FortranAPointerAssociate(%[[CONV_P]], %[[RP_BOX_NONE]]) {{.*}} : (!fir.ref<!fir.box<none>>, !fir.box<none>) -> none
 ! CHECK: return
 
 ! Test that the fir.dispatch operation is created with the correct pass object