diff --git a/flang/lib/Optimizer/Builder/IntrinsicCall.cpp b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
--- a/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
+++ b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
@@ -4035,10 +4035,18 @@
   mlir::Value fsourceCast = fsource;
   if (fir::isPolymorphicType(tsource.getType()) &&
       !fir::isPolymorphicType(fsource.getType())) {
-    tsourceCast = builder.createConvert(loc, fsource.getType(), tsource);
+    tsourceCast = builder.create<fir::ReboxOp>(loc, fsource.getType(), tsource,
+                                               /*shape*/ mlir::Value{},
+                                               /*slice=*/mlir::Value{});
+
+    // builder.createConvert(loc, fsource.getType(), tsource);
   } else if (!fir::isPolymorphicType(tsource.getType()) &&
              fir::isPolymorphicType(fsource.getType())) {
-    fsourceCast = builder.createConvert(loc, tsource.getType(), fsource);
+    fsourceCast = builder.create<fir::ReboxOp>(loc, tsource.getType(), fsource,
+                                               /*shape*/ mlir::Value{},
+                                               /*slice=*/mlir::Value{});
+
+    // fsourceCast = builder.createConvert(loc, tsource.getType(), fsource);
   } else {
     // FSOURCE and TSOURCE are not polymorphic.
     // FSOURCE has the same type as TSOURCE, but they may not have the same MLIR
diff --git a/flang/test/Lower/polymorphic-temp.f90 b/flang/test/Lower/polymorphic-temp.f90
--- a/flang/test/Lower/polymorphic-temp.f90
+++ b/flang/test/Lower/polymorphic-temp.f90
@@ -222,7 +222,7 @@
 ! CHECK: %[[LOAD_I:.*]] = fir.load %[[I]] : !fir.ref<i32>
 ! CHECK: %[[C1:.*]] = arith.constant 1 : i32
 ! CHECK: %[[CMPI:.*]] = arith.cmpi eq, %[[LOAD_I]], %[[C1]] : i32
-! CHECK: %[[A_CONV:.*]] = fir.convert %[[LOAD_A]] : (!fir.class<!fir.heap<!fir.type<_QMpoly_tmpTp1{a:i32}>>>) -> !fir.box<!fir.heap<!fir.type<_QMpoly_tmpTp1{a:i32}>>>
-! CHECK: %{{.*}} = arith.select %[[CMPI]], %[[A_CONV]], %[[LOAD_B]] : !fir.box<!fir.heap<!fir.type<_QMpoly_tmpTp1{a:i32}>>>
+! CHECK: %[[A_REBOX:.*]] = fir.rebox %[[LOAD_A]] : (!fir.class<!fir.heap<!fir.type<_QMpoly_tmpTp1{a:i32}>>>) -> !fir.box<!fir.heap<!fir.type<_QMpoly_tmpTp1{a:i32}>>> 
+! CHECK: %{{.*}} = arith.select %[[CMPI]], %[[A_REBOX]], %[[LOAD_B]] : !fir.box<!fir.heap<!fir.type<_QMpoly_tmpTp1{a:i32}>>>
 
 end module