diff --git a/flang/lib/Optimizer/Builder/MutableBox.cpp b/flang/lib/Optimizer/Builder/MutableBox.cpp
--- a/flang/lib/Optimizer/Builder/MutableBox.cpp
+++ b/flang/lib/Optimizer/Builder/MutableBox.cpp
@@ -28,7 +28,7 @@
                                    mlir::Value addr, mlir::ValueRange lbounds,
                                    mlir::ValueRange extents,
                                    mlir::ValueRange lengths) {
-  if (addr.getType().isa<fir::BoxType>())
+  if (addr.getType().isa<fir::BaseBoxType>())
     // The entity is already boxed.
     return builder.createConvert(loc, box.getBoxTy(), addr);
 
diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -3116,7 +3116,7 @@
   mlir::LogicalResult
   matchAndRewrite(fir::StoreOp store, OpAdaptor adaptor,
                   mlir::ConversionPatternRewriter &rewriter) const override {
-    if (store.getValue().getType().isa<fir::BoxType>()) {
+    if (store.getValue().getType().isa<fir::BaseBoxType>()) {
       // fir.box value is actually in memory, load it first before storing it.
       mlir::Location loc = store.getLoc();
       mlir::Type boxPtrTy = adaptor.getOperands()[0].getType();
diff --git a/flang/test/Lower/allocatable-polymorphic.f90 b/flang/test/Lower/allocatable-polymorphic.f90
--- a/flang/test/Lower/allocatable-polymorphic.f90
+++ b/flang/test/Lower/allocatable-polymorphic.f90
@@ -356,6 +356,14 @@
 
 ! CHECK: %[[C4_CAST:.*]] = fir.convert %[[C4]] : (!fir.ref<!fir.class<!fir.heap<!fir.array<?x!fir.type<_QMpolyTp1{a:i32,b:i32}>>>>>) -> !fir.ref<!fir.box<none>>
 ! CHECK: %{{.*}} = fir.call @_FortranAAllocatableDeallocate(%[[C4_CAST]], %{{.*}}, %{{.*}}, %{{.*}}, %{{.*}}) : (!fir.ref<!fir.box<none>>, i1, !fir.box<none>, !fir.ref<i8>, i32) -> i32
+
+  ! Test code generation of deallocate
+  subroutine test_deallocate()
+    class(p1), allocatable :: p
+
+    allocate(p)
+    deallocate(p)
+  end subroutine
 end module
 
 program test_alloc
@@ -420,3 +428,40 @@
 ! LLVM: %[[BOX1:.*]] = insertvalue { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[BOX0]], ptr %{{.*}}, 0
 ! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[BOX1]], ptr %{{.*}}
 ! LLVM: call void %{{.*}}(ptr %{{.*}})
+
+
+! Check code generation of a allocate/deallocate sequence on polymorphic
+! allocatable.
+
+! LLVM-LABEL: define void @_QMpolyPtest_deallocate()
+! LLVM: %[[ALLOCA1:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }
+! LLVM: %[[ALLOCA2:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }
+! LLVM: %[[ALLOCA3:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }
+! LLVM: %[[ALLOCA4:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }
+! LLVM: %[[DESC:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, i64 1
+! LLVM: %[[BASE_ADDR:.*]] = alloca ptr, i64 1
+! LLVM: store ptr null, ptr %[[BASE_ADDR]]
+! LLVM: %[[LOAD_BASE_ADDR:.*]] = load ptr, ptr %[[BASE_ADDR]]
+! LLVM: %[[BOX0:.*]] = insertvalue { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } { ptr undef, i64 ptrtoint (ptr getelementptr (%_QMpolyTp1, ptr null, i32 1) to i64), i32 20180515, i8 0, i8 42, i8 2, i8 1, ptr @_QMpolyE.dt.p1, [1 x i64] undef }, ptr %[[LOAD_BASE_ADDR]], 0
+! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[BOX0]], ptr %[[ALLOCA4]]
+! LLVM: %[[LOAD:.*]] = load { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %[[ALLOCA4]]
+! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[LOAD]], ptr %[[DESC]]
+! LLVM: %{{.*}} = call {} @_FortranAAllocatableInitDerived(ptr %[[DESC]], ptr @_QMpolyE.dt.p1, i32 0, i32 0)
+! LLVM: %{{.*}} = call i32 @_FortranAAllocatableAllocate(ptr %[[DESC]], i1 false, ptr null, ptr @_QQcl.{{.*}}, i32 {{.*}})
+! LLVM: %[[LOAD_DESC:.*]] = load { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %[[DESC]]
+! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[LOAD_DESC]], ptr %[[ALLOCA3]]
+! LLVM: %[[BASE_ADDR_GEP:.*]] = getelementptr { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %[[ALLOCA3]], i32 0, i32 0
+! LLVM: %[[LOAD_BASE_ADDR:.*]] = load ptr, ptr %[[BASE_ADDR_GEP]]
+! LLVM: store ptr %[[LOAD_BASE_ADDR]], ptr %[[BASE_ADDR]]
+! LLVM: %[[LOAD_BASE_ADDR:.*]] = load ptr, ptr %[[BASE_ADDR]]
+! LLVM: %[[BOX0:.*]] = insertvalue { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } { ptr undef, i64 ptrtoint (ptr getelementptr (%_QMpolyTp1, ptr null, i32 1) to i64), i32 20180515, i8 0, i8 42, i8 2, i8 1, ptr @_QMpolyE.dt.p1, [1 x i64] undef }, ptr %[[LOAD_BASE_ADDR]], 0
+! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[BOX0]], ptr %[[ALLOCA2]]
+! LLVM: %[[LOAD:.*]] = load { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %[[ALLOCA2]]
+! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[LOAD]], ptr %[[DESC]]
+! LLVM: %{{.*}} = call i32 @_FortranAAllocatableDeallocate(ptr %[[DESC]], i1 false, ptr null, ptr @_QQcl.{{.*}}, i32 {{.*}})
+! LLVM: %[[LOAD_DESC:.*]] = load { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %[[DESC]]
+! LLVM: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[LOAD_DESC]], ptr %[[ALLOCA1]]
+! LLVM: %[[BASE_ADDR_GEP:.*]] = getelementptr { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %1, i32 0, i32 0
+! LLVM: %[[LOAD_BASE_ADDR:.*]] = load ptr, ptr %[[BASE_ADDR_GEP]]
+! LLVM: store ptr %[[LOAD_BASE_ADDR]], ptr %[[BASE_ADDR]]
+! LLVM: ret void