diff --git a/src/CppParser/Bindings/CSharp/i686-apple-darwin12.4.0/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/i686-apple-darwin12.4.0/CppSharp.CppParser.cs
index 7b874516..e08c4ada 100644
--- a/src/CppParser/Bindings/CSharp/i686-apple-darwin12.4.0/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/i686-apple-darwin12.4.0/CppSharp.CppParser.cs
@@ -40250,18 +40250,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internal*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40600,18 +40601,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> PackIndex
+                public System.Nullable<uint> PackIndex
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->packIndex = *(global::Std.Optional.__Internal*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41306,18 +41308,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internal*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc-d/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc-d/CppSharp.CppParser.cs
index e55ca297..be814140 100644
--- a/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc-d/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc-d/CppSharp.CppParser.cs
@@ -40265,8 +40265,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40617,8 +40616,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->packIndex = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41325,8 +41323,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc/CppSharp.CppParser.cs
index fba42987..43fa89db 100644
--- a/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/i686-pc-win32-msvc/CppSharp.CppParser.cs
@@ -40265,8 +40265,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40617,8 +40616,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->packIndex = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41325,8 +41323,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/x86_64-apple-darwin12.4.0/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/x86_64-apple-darwin12.4.0/CppSharp.CppParser.cs
index 4cd7073e..a6569a15 100644
--- a/src/CppParser/Bindings/CSharp/x86_64-apple-darwin12.4.0/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/x86_64-apple-darwin12.4.0/CppSharp.CppParser.cs
@@ -40249,18 +40249,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internal*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40599,18 +40600,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> PackIndex
+                public System.Nullable<uint> PackIndex
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->packIndex = *(global::Std.Optional.__Internal*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41305,18 +41307,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internal*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/x86_64-linux-gnu-cxx11abi/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/x86_64-linux-gnu-cxx11abi/CppSharp.CppParser.cs
index 25616ab2..2c714c4f 100644
--- a/src/CppParser/Bindings/CSharp/x86_64-linux-gnu-cxx11abi/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/x86_64-linux-gnu-cxx11abi/CppSharp.CppParser.cs
@@ -40249,18 +40249,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internalc__N_std_S_optional__i*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40599,18 +40600,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> PackIndex
+                public System.Nullable<uint> PackIndex
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->packIndex = *(global::Std.Optional.__Internalc__N_std_S_optional__i*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41305,18 +41307,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internalc__N_std_S_optional__i*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/x86_64-linux-gnu/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/x86_64-linux-gnu/CppSharp.CppParser.cs
index 8a48808a..8880b885 100644
--- a/src/CppParser/Bindings/CSharp/x86_64-linux-gnu/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/x86_64-linux-gnu/CppSharp.CppParser.cs
@@ -40249,18 +40249,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internalc__N_std_S_optional__i*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40599,18 +40600,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> PackIndex
+                public System.Nullable<uint> PackIndex
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->packIndex));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->packIndex = *(global::Std.Optional.__Internalc__N_std_S_optional__i*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41305,18 +41307,19 @@ namespace CppSharp
                     }
                 }
 
-                public global::Std.Optional<uint> NumExpansions
+                public System.Nullable<uint> NumExpansions
                 {
                     get
                     {
-                        return global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        var __optionalRet0 = global::Std.Optional<uint>.__CreateInstance(new __IntPtr(&((__Internal*)__Instance)->numExpansions));
+                        if (!__optionalRet0.HasValue)
+                            return null;
+                        return global::Std.OptionalExtensions.Value(__optionalRet0);
                     }
 
                     set
                     {
-                        if (ReferenceEquals(value, null))
-                            throw new global::System.ArgumentNullException("value", "Cannot be null because it is passed by value.");
-                        ((__Internal*)__Instance)->numExpansions = *(global::Std.Optional.__Internalc__N_std_S_optional__i*) value.__Instance;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc-d/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc-d/CppSharp.CppParser.cs
index 2902e3b9..f80fc9d1 100644
--- a/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc-d/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc-d/CppSharp.CppParser.cs
@@ -40327,8 +40327,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40681,8 +40680,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->packIndex = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41390,8 +41388,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
diff --git a/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc/CppSharp.CppParser.cs b/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc/CppSharp.CppParser.cs
index fff44be8..877c82a5 100644
--- a/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc/CppSharp.CppParser.cs
+++ b/src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc/CppSharp.CppParser.cs
@@ -40327,8 +40327,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }
@@ -40681,8 +40680,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->packIndex = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
 
@@ -41390,8 +41388,7 @@ namespace CppSharp
 
                     set
                     {
-                        throw new NotImplementedException();
-                        ((__Internal*)__Instance)->numExpansions = null;
+                        throw new System.NotImplementedException("Setting std::optional is currently not supported");
                     }
                 }
             }