diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -4237,14 +4237,21 @@
     }
 
     // Defer address space conversion to the third conversion.
+    // FIXME: If PerformImplicitConversion did not try to pass the final
+    // destination type to every conversion function in here, this would not
+    // be necessary since the address space conversion would be handled as
+    // a qualification conversion instead.
     QualType FromPteeType = From->getType()->getPointeeType();
     QualType ToPteeType = ToType->getPointeeType();
     QualType NewToType = ToType;
     if (!FromPteeType.isNull() && !ToPteeType.isNull() &&
         FromPteeType.getAddressSpace() != ToPteeType.getAddressSpace()) {
-      NewToType = Context.removeAddrSpaceQualType(ToPteeType);
-      NewToType = Context.getAddrSpaceQualType(NewToType,
-                                               FromPteeType.getAddressSpace());
+      NewToType =
+          Context.removeAddrSpaceQualType(ToPteeType.getCanonicalType());
+      if (FromPteeType.getAddressSpace() != LangAS::Default)
+        NewToType = Context.getAddrSpaceQualType(
+            NewToType, FromPteeType.getAddressSpace());
+
       if (ToType->isObjCObjectPointerType())
         NewToType = Context.getObjCObjectPointerType(NewToType);
       else if (ToType->isBlockPointerType())
diff --git a/clang/test/CodeGenCXX/address-space-cast.cpp b/clang/test/CodeGenCXX/address-space-cast.cpp
--- a/clang/test/CodeGenCXX/address-space-cast.cpp
+++ b/clang/test/CodeGenCXX/address-space-cast.cpp
@@ -6,6 +6,16 @@
 void func_pvoid(__private__ void *x);
 void func_pint(__private__ int *x);
 
+class Base {
+};
+
+class Derived : public Base {
+};
+
+void fn(Derived *p) {
+  __private__ Base *b = (__private__ Base *)p;
+}
+
 void test_cast(char *gen_char_ptr, void *gen_void_ptr, int *gen_int_ptr) {
   // CHECK: %[[cast:.*]] = addrspacecast i8* %{{.*}} to i8 addrspace(5)*
   // CHECK-NEXT: store i8 addrspace(5)* %[[cast]]