diff --git a/flang/include/flang/Optimizer/Dialect/FIROps.td b/flang/include/flang/Optimizer/Dialect/FIROps.td
--- a/flang/include/flang/Optimizer/Dialect/FIROps.td
+++ b/flang/include/flang/Optimizer/Dialect/FIROps.td
@@ -824,12 +824,12 @@
   }];
 
   let arguments = (ins
-    fir_BoxType:$box,
+    BoxOrClassType:$box,
     Optional<AnyShapeOrShiftType>:$shape,
     Optional<fir_SliceType>:$slice
   );
 
-  let results = (outs fir_BoxType);
+  let results = (outs BoxOrClassType);
 
   let assemblyFormat = [{
     $box (`(` $shape^ `)`)? (`[` $slice^ `]`)? attr-dict `:` functional-type(operands, results)
diff --git a/flang/lib/Optimizer/Builder/FIRBuilder.cpp b/flang/lib/Optimizer/Builder/FIRBuilder.cpp
--- a/flang/lib/Optimizer/Builder/FIRBuilder.cpp
+++ b/flang/lib/Optimizer/Builder/FIRBuilder.cpp
@@ -325,6 +325,11 @@
     return create<fir::BoxAddrOp>(loc, toTy, val);
   }
 
+  if (fir::isPolymorphicType(fromTy) && fir::isPolymorphicType(toTy)) {
+    return create<fir::ReboxOp>(loc, toTy, val, mlir::Value{},
+                                /*slice=*/mlir::Value{});
+  }
+
   return createConvert(loc, toTy, val);
 }
 
diff --git a/flang/test/Fir/invalid.fir b/flang/test/Fir/invalid.fir
--- a/flang/test/Fir/invalid.fir
+++ b/flang/test/Fir/invalid.fir
@@ -20,7 +20,7 @@
 func.func @bad_rebox_1(%arg0: !fir.ref<!fir.array<?x?xf32>>) {
   %c10 = arith.constant 10 : index
   %0 = fir.shape %c10 : (index) -> !fir.shape<1>
-  // expected-error@+1{{op operand #0 must be The type of a Fortran descriptor, but got '!fir.ref<!fir.array<?x?xf32>>'}}
+  // expected-error@+1{{op operand #0 must be box or class, but got '!fir.ref<!fir.array<?x?xf32>>'}}
   %1 = fir.rebox %arg0(%0) : (!fir.ref<!fir.array<?x?xf32>>, !fir.shape<1>) -> !fir.box<!fir.array<?xf32>>
   return
 }
@@ -30,7 +30,7 @@
 func.func @bad_rebox_2(%arg0: !fir.box<!fir.array<?x?xf32>>) {
   %c10 = arith.constant 10 : index
   %0 = fir.shape %c10 : (index) -> !fir.shape<1>
-  // expected-error@+1{{op result #0 must be The type of a Fortran descriptor, but got '!fir.ref<!fir.array<?xf32>>'}}
+  // expected-error@+1{{op result #0 must be box or class, but got '!fir.ref<!fir.array<?xf32>>'}}
   %1 = fir.rebox %arg0(%0) : (!fir.box<!fir.array<?x?xf32>>, !fir.shape<1>) -> !fir.ref<!fir.array<?xf32>>
   return
 }
diff --git a/flang/test/Lower/dispatch.f90 b/flang/test/Lower/dispatch.f90
--- a/flang/test/Lower/dispatch.f90
+++ b/flang/test/Lower/dispatch.f90
@@ -130,6 +130,28 @@
 ! CHECK: %{{.*}} = fir.dispatch "p1_fct3_arg0"(%[[P]] : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) (%[[P]] : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) -> f32 {pass_arg_pos = 0 : i32}
 ! CHECK: %{{.*}} = fir.dispatch "p1_fct4_arg1"(%[[P]] : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) (%{{.*}}, %[[P]] : !fir.ref<i32>, !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) -> f32 {pass_arg_pos = 1 : i32}
 
+    subroutine check_dispatch_scalar_allocatable(p)
+      class(p1), allocatable :: p
+      call p%tbp_pass()
+    end subroutine
+
+! CHECK-LABEL: func.func @_QMcall_dispatchPcheck_dispatch_scalar_allocatable(
+! CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.class<!fir.heap<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>>> {fir.bindc_name = "p"}) {
+! CHECK: %[[LOAD:.*]] = fir.load %[[ARG0]] : !fir.ref<!fir.class<!fir.heap<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>>>
+! CHECK: %[[REBOX:.*]] = fir.rebox %[[LOAD]] : (!fir.class<!fir.heap<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>>) -> !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>
+! CHECK: fir.dispatch "tbp_pass"(%[[REBOX]] : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) (%1 : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) {pass_arg_pos = 0 : i32}
+
+    subroutine check_dispatch_scalar_pointer(p)
+      class(p1), pointer :: p
+      call p%tbp_pass()
+    end subroutine
+
+! CHECK-LABEL: func.func @_QMcall_dispatchPcheck_dispatch_scalar_pointer(
+! CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.class<!fir.ptr<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>>> {fir.bindc_name = "p"}) {
+! CHECK: %[[LOAD:.*]] = fir.load %[[ARG0]] : !fir.ref<!fir.class<!fir.ptr<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>>>
+! CHECK: %[[REBOX:.*]] = fir.rebox %[[LOAD]] : (!fir.class<!fir.ptr<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>>) -> !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>
+! CHECK: fir.dispatch "tbp_pass"(%[[REBOX]] : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) (%1 : !fir.class<!fir.type<_QMcall_dispatchTp1{a:i32,b:i32}>>) {pass_arg_pos = 0 : i32}
+
 ! ------------------------------------------------------------------------------
 ! Test that direct call is emitted when the type is known
 ! ------------------------------------------------------------------------------