diff --git a/flang/lib/Lower/ConvertExpr.cpp b/flang/lib/Lower/ConvertExpr.cpp
--- a/flang/lib/Lower/ConvertExpr.cpp
+++ b/flang/lib/Lower/ConvertExpr.cpp
@@ -2970,8 +2970,9 @@
       return fir::factory::CharacterExprHelper{builder, loc}.createEmbox(
           *charBox);
     }
-    if (argType.isa<fir::BoxType>()) {
-      mlir::Value box = builder.createBox(loc, value);
+    if (argType.isa<fir::BaseBoxType>()) {
+      mlir::Value box =
+          builder.createBox(loc, value, argType.isa<fir::ClassType>());
       return builder.createConvert(loc, argType, box);
     }
     // Simple pass by address.
@@ -7171,7 +7172,7 @@
 }
 
 bool isParentComponent(const Fortran::lower::SomeExpr &expr) {
-  if (const Fortran::semantics::Symbol * symbol{GetLastSymbol(expr)}) {
+  if (const Fortran::semantics::Symbol *symbol{GetLastSymbol(expr)}) {
     if (symbol->test(Fortran::semantics::Symbol::Flag::ParentComp))
       return true;
   }
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
@@ -8,6 +8,8 @@
     integer :: b
   contains
     procedure :: print
+    procedure :: assign_p1_int
+    generic :: assignment(=) => assign_p1_int
   end type
 
   type, extends(p1) :: p2
@@ -30,6 +32,13 @@
 
   contains
 
+  elemental subroutine assign_p1_int(lhs, rhs)
+    class(p1), intent(inout) :: lhs
+    integer, intent(in) :: rhs
+    lhs%a = rhs
+    lhs%b = rhs
+  End Subroutine
+
   ! Test correct access to polymorphic entity component.
   subroutine component_access(p)
     class(p1) :: p
@@ -375,4 +384,33 @@
 ! CHECK: %[[ARG2:.*]] = fir.convert %[[BOXED_BOUND_ARRAY]] : (!fir.box<!fir.array<2xi64>>) -> !fir.box<none>
 ! CHECK: %{{.*}} = fir.call @_FortranAPointerAssociateRemapping(%[[ARG0]], %[[ARG1]], %[[ARG2]], %{{.*}}, %{{.*}}) {{.*}} : (!fir.ref<!fir.box<none>>, !fir.box<none>, !fir.box<none>, !fir.ref<i8>, i32) -> none
 
+  subroutine test_elemental_assign()
+    type(p1) :: pa(3)
+    pa = [ 1, 2, 3 ]
+  end subroutine
+
+! CHECK-LABEL: func.func @_QMpolymorphic_testPtest_elemental_assign() {
+! CHECK: %[[INT:.*]] = fir.alloca i32
+! CHECK: %[[C3_0:.*]] = arith.constant 3 : index
+! CHECK: %[[PA:.*]] = fir.alloca !fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>> {bindc_name = "pa", uniq_name = "_QMpolymorphic_testFtest_elemental_assignEpa"}
+! CHECK: %[[SHAPE:.*]] = fir.shape %[[C3_0]] : (index) -> !fir.shape<1>
+! CHECK: %[[LOAD_PA:.*]] = fir.array_load %[[PA]](%[[SHAPE]]) : (!fir.ref<!fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>>, !fir.shape<1>) -> !fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
+! CHECK: %[[ADDR_INT:.*]] = fir.address_of(@_QQro.3xi4.{{.*}}) : !fir.ref<!fir.array<3xi32>>
+! CHECK: %[[C3:.*]] = arith.constant 3 : index
+! CHECK: %[[SHAPE:.*]] = fir.shape %[[C3]] : (index) -> !fir.shape<1>
+! CHECK: %[[LOAD_INT_ARRAY:.*]] = fir.array_load %[[ADDR_INT]](%[[SHAPE]]) : (!fir.ref<!fir.array<3xi32>>, !fir.shape<1>) -> !fir.array<3xi32>
+! CHECK: %[[C1:.*]] = arith.constant 1 : index
+! CHECK: %[[C0:.*]] = arith.constant 0 : index
+! CHECK: %[[UB:.*]] = arith.subi %[[C3_0]], %[[C1]] : index
+! CHECK: %[[DO_RES:.*]] = fir.do_loop %[[ARG0:.*]] = %[[C0]] to %[[UB]] step %[[C1]] unordered iter_args(%[[ARG1:.*]] = %[[LOAD_PA]]) -> (!fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) {
+! CHECK:   %[[FETCH_INT:.*]] = fir.array_fetch %[[LOAD_INT_ARRAY]], %[[ARG0]] : (!fir.array<3xi32>, index) -> i32
+! CHECK:   %[[ARRAY_MOD:.*]]:2 = fir.array_modify %[[ARG1]], %[[ARG0]] : (!fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>, index) -> (!fir.ref<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>, !fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>)
+! CHECK:   %[[EMBOXED:.*]] = fir.embox %10#0 : (!fir.ref<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) -> !fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
+! CHECK:   fir.store %[[FETCH_INT]] to %[[INT]] : !fir.ref<i32>
+! CHECK:   fir.call @_QMpolymorphic_testPassign_p1_int(%[[EMBOXED]], %[[INT]]) fastmath<contract> : (!fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>, !fir.ref<i32>) -> ()
+! CHECK:   fir.result %[[ARRAY_MOD]]#1 : !fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
+! CHECK: }
+! CHECK: fir.array_merge_store %[[LOAD_PA]], %[[DO_RES]] to %[[PA]] : !fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>, !fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>, !fir.ref<!fir.array<3x!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>>
+! CHECK: return
+
 end module