diff --git a/CHANGES.current b/CHANGES.current
index 2fed37737..bb16fef2d 100644
--- a/CHANGES.current
+++ b/CHANGES.current
@@ -7,6 +7,11 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-08-05: wsfulton
+            [D] Fix occasional undefined behaviour with inheritance hierarchies, particularly
+            when using virtual inheritance as the pointers weren't correctly upcast from derived
+            class to base class when stored in the base's proxy class.
+
 2022-08-05: wsfulton
             [D] Add support for std::unique_ptr in std_unique_ptr.i.
             Add support for std::auto_ptr in std_auto_ptr.i.
diff --git a/Examples/test-suite/cpp11_std_unique_ptr.i b/Examples/test-suite/cpp11_std_unique_ptr.i
index 49c85d6aa..0549a7b45 100644
--- a/Examples/test-suite/cpp11_std_unique_ptr.i
+++ b/Examples/test-suite/cpp11_std_unique_ptr.i
@@ -10,6 +10,7 @@
 %inline %{
 #include <memory>
 #include <string>
+//#include <iostream>
 #include "swig_examples_lock.h"
 
 class Klass {
@@ -53,8 +54,18 @@ struct KlassInheritance : virtual Klass {
   }
 };
 
+std::string useKlassRawPtr(Klass* k) {
+//  std::cout << "useKlassRawPtr " << std::hex << (Klass*)k << std::endl;
+  std::string s(k->getLabel());
+//  std::cout << "useKlassRawPtr string: " << s << std::endl;
+  return s;
+}
+
 std::string takeKlassUniquePtr(std::unique_ptr<Klass> k) {
-  return std::string(k->getLabel());
+//  std::cout << "takeKlassUniquePtr " << std::hex << (Klass*)k.get() << std::endl;
+  std::string s(k->getLabel());
+//  std::cout << "takeKlassUniquePtr string: " << s << std::endl;
+  return s;
 }
 
 bool is_nullptr(Klass *p) {
diff --git a/Examples/test-suite/d/cpp11_std_unique_ptr_runme.1.d b/Examples/test-suite/d/cpp11_std_unique_ptr_runme.1.d
index 7730f255f..5aee10727 100644
--- a/Examples/test-suite/d/cpp11_std_unique_ptr_runme.1.d
+++ b/Examples/test-suite/d/cpp11_std_unique_ptr_runme.1.d
@@ -13,6 +13,16 @@ void checkCount(int expected_count) {
 }
 
 void main() {
+  // Test raw pointer handling involving virtual inheritance
+  {
+    scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
+    checkCount(1);
+    string s = useKlassRawPtr(kini);
+    if (s != "KlassInheritanceInput")
+      throw new Exception("Incorrect string: " ~ s);
+  }
+  checkCount(0);
+
   // unique_ptr as input
   {
     scope Klass kin = new Klass("KlassInput");
@@ -65,7 +75,6 @@ void main() {
   }
   checkCount(0);
 
-  /*
   {
     scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
     checkCount(1);
@@ -77,7 +86,6 @@ void main() {
       throw new Exception("is_nullptr failed");
   } // dispose should not fail, even though already deleted
   checkCount(0);
-  */
 
   // unique_ptr as output
   Klass k1 = makeKlassUniquePtr("first");
diff --git a/Examples/test-suite/d/cpp11_std_unique_ptr_runme.2.d b/Examples/test-suite/d/cpp11_std_unique_ptr_runme.2.d
index 7730f255f..5aee10727 100644
--- a/Examples/test-suite/d/cpp11_std_unique_ptr_runme.2.d
+++ b/Examples/test-suite/d/cpp11_std_unique_ptr_runme.2.d
@@ -13,6 +13,16 @@ void checkCount(int expected_count) {
 }
 
 void main() {
+  // Test raw pointer handling involving virtual inheritance
+  {
+    scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
+    checkCount(1);
+    string s = useKlassRawPtr(kini);
+    if (s != "KlassInheritanceInput")
+      throw new Exception("Incorrect string: " ~ s);
+  }
+  checkCount(0);
+
   // unique_ptr as input
   {
     scope Klass kin = new Klass("KlassInput");
@@ -65,7 +75,6 @@ void main() {
   }
   checkCount(0);
 
-  /*
   {
     scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
     checkCount(1);
@@ -77,7 +86,6 @@ void main() {
       throw new Exception("is_nullptr failed");
   } // dispose should not fail, even though already deleted
   checkCount(0);
-  */
 
   // unique_ptr as output
   Klass k1 = makeKlassUniquePtr("first");
diff --git a/Examples/test-suite/d/li_std_auto_ptr_runme.1.d b/Examples/test-suite/d/li_std_auto_ptr_runme.1.d
index 76c81ffc8..3b51ba3ce 100644
--- a/Examples/test-suite/d/li_std_auto_ptr_runme.1.d
+++ b/Examples/test-suite/d/li_std_auto_ptr_runme.1.d
@@ -13,6 +13,16 @@ void checkCount(int expected_count) {
 }
 
 void main() {
+  // Test raw pointer handling involving virtual inheritance
+  {
+    scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
+    checkCount(1);
+    string s = useKlassRawPtr(kini);
+    if (s != "KlassInheritanceInput")
+      throw new Exception("Incorrect string: " ~ s);
+  }
+  checkCount(0);
+
   // auto_ptr as input
   {
     scope Klass kin = new Klass("KlassInput");
@@ -65,7 +75,6 @@ void main() {
   }
   checkCount(0);
 
-  /*
   {
     scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
     checkCount(1);
@@ -77,7 +86,6 @@ void main() {
       throw new Exception("is_nullptr failed");
   } // dispose should not fail, even though already deleted
   checkCount(0);
-  */
 
   // auto_ptr as output
   Klass k1 = makeKlassAutoPtr("first");
diff --git a/Examples/test-suite/d/li_std_auto_ptr_runme.2.d b/Examples/test-suite/d/li_std_auto_ptr_runme.2.d
index 76c81ffc8..38efa3d7d 100644
--- a/Examples/test-suite/d/li_std_auto_ptr_runme.2.d
+++ b/Examples/test-suite/d/li_std_auto_ptr_runme.2.d
@@ -13,6 +13,17 @@ void checkCount(int expected_count) {
 }
 
 void main() {
+  // Test raw pointer handling involving virtual inheritance
+  {
+    scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
+    checkCount(1);
+    string s = useKlassRawPtr(kini);
+    checkCount(1);
+    if (s != "KlassInheritanceInput")
+      throw new Exception("Incorrect string: " ~ s);
+  }
+  checkCount(0);
+
   // auto_ptr as input
   {
     scope Klass kin = new Klass("KlassInput");
@@ -65,7 +76,6 @@ void main() {
   }
   checkCount(0);
 
-  /*
   {
     scope KlassInheritance kini = new KlassInheritance("KlassInheritanceInput");
     checkCount(1);
@@ -77,7 +87,6 @@ void main() {
       throw new Exception("is_nullptr failed");
   } // dispose should not fail, even though already deleted
   checkCount(0);
-  */
 
   // auto_ptr as output
   Klass k1 = makeKlassAutoPtr("first");
diff --git a/Examples/test-suite/li_std_auto_ptr.i b/Examples/test-suite/li_std_auto_ptr.i
index afa4782c3..5f3b7724f 100644
--- a/Examples/test-suite/li_std_auto_ptr.i
+++ b/Examples/test-suite/li_std_auto_ptr.i
@@ -15,6 +15,7 @@
 #if defined(SWIGCSHARP) || defined(SWIGJAVA) || defined(SWIGPYTHON) || defined(SWIGRUBY) || defined(SWIGPERL) || defined(SWIGTCL) || defined(SWIGOCTAVE) || defined(SWIGJAVASCRIPT) || defined(SWIGD)
 
 %include "std_string.i"
+//#include <iostream>
 %include "std_auto_ptr.i"
 
 %auto_ptr(Klass)
@@ -100,10 +101,21 @@ struct KlassInheritance : virtual Klass {
   }
 };
 
-std::string takeKlassAutoPtr(std::auto_ptr<Klass> k) {
-  return std::string(k->getLabel());
+std::string useKlassRawPtr(Klass* k) {
+//  std::cout << "useKlassRawPtr " << std::hex << (Klass*)k << std::endl;
+  std::string s(k->getLabel());
+//  std::cout << "useKlassRawPtr string: " << s << std::endl;
+  return s;
 }
 
+std::string takeKlassAutoPtr(std::auto_ptr<Klass> k) {
+//  std::cout << "takeKlassAutoPtr " << std::hex << (Klass*)k.get() << std::endl;
+  std::string s(k->getLabel());
+//  std::cout << "takeKlassAutoPtr string: " << s << std::endl;
+  return s;
+}
+
+
 bool is_nullptr(Klass *p) {
   return p == 0;
 }
diff --git a/Source/Modules/d.cxx b/Source/Modules/d.cxx
index ff32dbf0b..c1f68da07 100644
--- a/Source/Modules/d.cxx
+++ b/Source/Modules/d.cxx
@@ -3402,7 +3402,7 @@ private:
     } else {
       Printv(upcasts_code,
 	"SWIGEXPORT ", baseclassname, " * ", upcast_wrapper_name,
-	  "(", baseclassname, " *objectRef) {\n",
+	  "(", classname, " *objectRef) {\n",
 	"    return (", baseclassname, " *)objectRef;\n"
 	"}\n",
 	"\n", NIL);