diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleUnix/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleUnix/CXXMethodDeclarationTest.cs
index 877fdd72..934ff19c 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleUnix/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleUnix/CXXMethodDeclarationTest.cs
@@ -483,10 +483,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
                 callConv = "ThisCall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"using System;
@@ -533,13 +535,13 @@ public int GetType(int objA, int objB)
 
         public partial struct Vtbl
         {{
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "new ")}IntPtr GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")};
 
-            [NativeTypeName(""int ()"")]
+            [NativeTypeName(""int (){nativeCallConv}"")]
             public IntPtr GetType1;
 
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "new " : "")}IntPtr GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")};
         }}
     }}
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleWindows/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleWindows/CXXMethodDeclarationTest.cs
index a4d02349..054d12b5 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleWindows/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpCompatibleWindows/CXXMethodDeclarationTest.cs
@@ -483,10 +483,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
                 callConv = "ThisCall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"using System;
@@ -533,13 +535,13 @@ public int GetType(int objA, int objB)
 
         public partial struct Vtbl
         {{
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "new ")}IntPtr GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")};
 
-            [NativeTypeName(""int ()"")]
+            [NativeTypeName(""int (){nativeCallConv}"")]
             public IntPtr GetType1;
 
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "new " : "")}IntPtr GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")};
         }}
     }}
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/CXXMethodDeclarationTest.cs
index 2dce96ea..e488d504 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/CXXMethodDeclarationTest.cs
@@ -422,7 +422,7 @@ public override Task NewKeywordVirtualTest()
             
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
@@ -464,10 +464,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
@@ -495,13 +497,13 @@ public int GetType(int objA, int objB)
 
         public partial struct Vtbl
         {{
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "new ")}delegate* unmanaged[{callConv}]<MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ", int" : "")}> GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")};
 
-            [NativeTypeName(""int ()"")]
+            [NativeTypeName(""int (){nativeCallConv}"")]
             public delegate* unmanaged[{callConv}]<MyStruct*, int> GetType1;
 
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "new " : "")}delegate* unmanaged[{callConv}]<MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : ", int")}> GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")};
         }}
     }}
@@ -773,7 +775,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
@@ -833,7 +835,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/FunctionDeclarationBodyImportTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/FunctionDeclarationBodyImportTest.cs
index 3c28d3fa..3a4b67cd 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/FunctionDeclarationBodyImportTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestUnix/FunctionDeclarationBodyImportTest.cs
@@ -500,7 +500,7 @@ struct MyStructB : MyStructA { };
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/CXXMethodDeclarationTest.cs
index 5362d7a7..ecaebcf5 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/CXXMethodDeclarationTest.cs
@@ -422,7 +422,7 @@ public override Task NewKeywordVirtualTest()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
@@ -464,10 +464,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
@@ -495,13 +497,13 @@ public int GetType(int objA, int objB)
 
         public partial struct Vtbl
         {{
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "new ")}delegate* unmanaged[{callConv}]<MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ", int" : "")}> GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")};
 
-            [NativeTypeName(""int ()"")]
+            [NativeTypeName(""int (){nativeCallConv}"")]
             public delegate* unmanaged[{callConv}]<MyStruct*, int> GetType1;
 
-            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"")]
+            [NativeTypeName(""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"")]
             public {(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "new " : "")}delegate* unmanaged[{callConv}]<MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : ", int")}> GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")};
         }}
     }}
@@ -773,7 +775,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
@@ -833,7 +835,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/FunctionDeclarationBodyImportTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/FunctionDeclarationBodyImportTest.cs
index 2538ded1..6584c70c 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/FunctionDeclarationBodyImportTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/CSharpLatestWindows/FunctionDeclarationBodyImportTest.cs
@@ -500,7 +500,7 @@ struct MyStructB : MyStructA { };
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"using System.Runtime.CompilerServices;
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleUnix/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleUnix/CXXMethodDeclarationTest.cs
index 58cd31b6..dd1fec06 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleUnix/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleUnix/CXXMethodDeclarationTest.cs
@@ -566,10 +566,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
                 callConv = "ThisCall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -644,13 +646,13 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
       </function>
       <vtbl>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"">IntPtr</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"">IntPtr</type>
         </field>
         <field name=""GetType1"" access=""public"">
-          <type native=""int ()"">IntPtr</type>
+          <type native=""int (){nativeCallConv}"">IntPtr</type>
         </field>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"">IntPtr</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"">IntPtr</type>
         </field>
       </vtbl>
     </struct>
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleWindows/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleWindows/CXXMethodDeclarationTest.cs
index 1e3385b5..3700e014 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleWindows/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlCompatibleWindows/CXXMethodDeclarationTest.cs
@@ -566,10 +566,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
                 callConv = "ThisCall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -644,13 +646,13 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
       </function>
       <vtbl>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"">IntPtr</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"">IntPtr</type>
         </field>
         <field name=""GetType1"" access=""public"">
-          <type native=""int ()"">IntPtr</type>
+          <type native=""int (){nativeCallConv}"">IntPtr</type>
         </field>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"">IntPtr</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"">IntPtr</type>
         </field>
       </vtbl>
     </struct>
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/CXXMethodDeclarationTest.cs
index 18f8a882..d16726cc 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/CXXMethodDeclarationTest.cs
@@ -475,7 +475,7 @@ public override Task NewKeywordVirtualTest()
             
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -530,10 +530,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -572,13 +574,13 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
       </function>
       <vtbl>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ", int" : "")}&gt;</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ", int" : "")}&gt;</type>
         </field>
         <field name=""GetType1"" access=""public"">
-          <type native=""int ()"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int&gt;</type>
+          <type native=""int (){nativeCallConv}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int&gt;</type>
         </field>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : ", int")}&gt;</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : ", int")}&gt;</type>
         </field>
       </vtbl>
     </struct>
@@ -885,7 +887,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -948,7 +950,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/FunctionDeclarationBodyImportTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/FunctionDeclarationBodyImportTest.cs
index 558e0130..21322de3 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/FunctionDeclarationBodyImportTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestUnix/FunctionDeclarationBodyImportTest.cs
@@ -582,7 +582,7 @@ struct MyStructB : MyStructA { };
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/CXXMethodDeclarationTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/CXXMethodDeclarationTest.cs
index 055a97a8..9bb0d332 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/CXXMethodDeclarationTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/CXXMethodDeclarationTest.cs
@@ -475,7 +475,7 @@ public override Task NewKeywordVirtualTest()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -530,10 +530,12 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
 };";
 
             var callConv = "Cdecl";
+            var nativeCallConv = "";
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
+                nativeCallConv = " __attribute__((thiscall))";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -572,13 +574,13 @@ public override Task NewKeywordVirtualWithExplicitVtblTest()
       </function>
       <vtbl>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "2" : "")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ", int" : "")}&gt;</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int, int)" : "int (int)")}{nativeCallConv}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ", int" : "")}&gt;</type>
         </field>
         <field name=""GetType1"" access=""public"">
-          <type native=""int ()"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int&gt;</type>
+          <type native=""int (){nativeCallConv}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int&gt;</type>
         </field>
         <field name=""GetType{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : "2")}"" access=""public"">
-          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : ", int")}&gt;</type>
+          <type native=""{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "int (int)" : "int (int, int)")}{nativeCallConv}"">delegate* unmanaged[{callConv}]&lt;MyStruct*, int, int{(RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "" : ", int")}&gt;</type>
         </field>
       </vtbl>
     </struct>
@@ -885,7 +887,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
@@ -948,7 +950,7 @@ virtual char MyInt8Method()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>
diff --git a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/FunctionDeclarationBodyImportTest.cs b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/FunctionDeclarationBodyImportTest.cs
index f19bfe4c..df5e80dd 100644
--- a/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/FunctionDeclarationBodyImportTest.cs
+++ b/tests/ClangSharp.PInvokeGenerator.UnitTests/XmlLatestWindows/FunctionDeclarationBodyImportTest.cs
@@ -582,7 +582,7 @@ struct MyStructB : MyStructA { };
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !Environment.Is64BitProcess)
             {
-                callConv = "ThisCall";
+                callConv = "Thiscall";
             }
 
             var expectedOutputContents = $@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes"" ?>