diff --git a/tests/generator-Tests/expected.xaji/AccessModifiers/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/AccessModifiers/__NamespaceMapping__.cs
index d7a37a175..da271fdcf 100644
--- a/tests/generator-Tests/expected.xaji/AccessModifiers/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/AccessModifiers/__NamespaceMapping__.cs
@@ -3,6 +3,7 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PP_V (IntPtr jnienv, IntPtr klass);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/Adapters/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/Adapters/__NamespaceMapping__.cs
index b3744898d..6a3cb3b07 100644
--- a/tests/generator-Tests/expected.xaji/Adapters/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/Adapters/__NamespaceMapping__.cs
@@ -3,7 +3,9 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PP_L (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/Android.Graphics.Color/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/Android.Graphics.Color/__NamespaceMapping__.cs
index b77cc8ae4..f21fe337f 100644
--- a/tests/generator-Tests/expected.xaji/Android.Graphics.Color/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/Android.Graphics.Color/__NamespaceMapping__.cs
@@ -3,7 +3,9 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PP_I (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPI_V (IntPtr jnienv, IntPtr klass, int p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/CSharpKeywords/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/CSharpKeywords/__NamespaceMapping__.cs
index 873216e5e..2531fbbdd 100644
--- a/tests/generator-Tests/expected.xaji/CSharpKeywords/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/CSharpKeywords/__NamespaceMapping__.cs
@@ -3,7 +3,9 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PP_L (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PPI_L (IntPtr jnienv, IntPtr klass, int p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/Core_Jar2Xml/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/Core_Jar2Xml/__NamespaceMapping__.cs
index 8400b35b2..420ab6f51 100644
--- a/tests/generator-Tests/expected.xaji/Core_Jar2Xml/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/Core_Jar2Xml/__NamespaceMapping__.cs
@@ -4,7 +4,9 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "android.text", Managed="Android.Text")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PPL_I (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/GenericArguments/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/GenericArguments/__NamespaceMapping__.cs
index e4861000c..35c4547b6 100644
--- a/tests/generator-Tests/expected.xaji/GenericArguments/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/GenericArguments/__NamespaceMapping__.cs
@@ -3,8 +3,11 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "com.google.android.exoplayer.drm", Managed="Com.Google.Android.Exoplayer.Drm")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate bool _JniMarshal_PPL_Z (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPLLIIL_V (IntPtr jnienv, IntPtr klass, IntPtr p0, IntPtr p1, int p2, int p3, IntPtr p4);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/InterfaceMethodsConflict/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/InterfaceMethodsConflict/__NamespaceMapping__.cs
index d7a37a175..da271fdcf 100644
--- a/tests/generator-Tests/expected.xaji/InterfaceMethodsConflict/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/InterfaceMethodsConflict/__NamespaceMapping__.cs
@@ -3,6 +3,7 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PP_V (IntPtr jnienv, IntPtr klass);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/NestedTypes/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/NestedTypes/__NamespaceMapping__.cs
index a7dc99417..72dd41701 100644
--- a/tests/generator-Tests/expected.xaji/NestedTypes/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/NestedTypes/__NamespaceMapping__.cs
@@ -3,6 +3,7 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PPI_L (IntPtr jnienv, IntPtr klass, int p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/NormalMethods/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/NormalMethods/__NamespaceMapping__.cs
index 871315e91..3f1acb70a 100644
--- a/tests/generator-Tests/expected.xaji/NormalMethods/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/NormalMethods/__NamespaceMapping__.cs
@@ -4,12 +4,19 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.util", Managed="Java.Util")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PP_I (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PP_L (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PP_V (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PPI_L (IntPtr jnienv, IntPtr klass, int p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPLIL_V (IntPtr jnienv, IntPtr klass, IntPtr p0, int p1, IntPtr p2);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PPLL_I (IntPtr jnienv, IntPtr klass, IntPtr p0, IntPtr p1);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/NormalProperties/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/NormalProperties/__NamespaceMapping__.cs
index 9378e8754..b8da138eb 100644
--- a/tests/generator-Tests/expected.xaji/NormalProperties/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/NormalProperties/__NamespaceMapping__.cs
@@ -3,9 +3,13 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PP_I (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PP_L (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPI_V (IntPtr jnienv, IntPtr klass, int p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/ParameterXPath/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/ParameterXPath/__NamespaceMapping__.cs
index 98846fdfd..11a58fa57 100644
--- a/tests/generator-Tests/expected.xaji/ParameterXPath/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/ParameterXPath/__NamespaceMapping__.cs
@@ -4,6 +4,7 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.util", Managed="Java.Util")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "xamarin.test", Managed="Xamarin.Test")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/Streams/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/Streams/__NamespaceMapping__.cs
index 3fd58207c..ce368cc40 100644
--- a/tests/generator-Tests/expected.xaji/Streams/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/Streams/__NamespaceMapping__.cs
@@ -3,15 +3,25 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.io", Managed="Java.IO")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PP_I (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PP_L (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PP_V (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate bool _JniMarshal_PP_Z (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPI_V (IntPtr jnienv, IntPtr klass, int p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate long _JniMarshal_PPJ_J (IntPtr jnienv, IntPtr klass, long p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PPL_I (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PPLII_I (IntPtr jnienv, IntPtr klass, IntPtr p0, int p1, int p2);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPLII_V (IntPtr jnienv, IntPtr klass, IntPtr p0, int p1, int p2);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/TestInterface/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/TestInterface/__NamespaceMapping__.cs
index 19abe220c..825ceb91a 100644
--- a/tests/generator-Tests/expected.xaji/TestInterface/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/TestInterface/__NamespaceMapping__.cs
@@ -5,11 +5,17 @@
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "test.me", Managed="Test.ME")]
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "", Managed="")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PP_L (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PP_V (IntPtr jnienv, IntPtr klass);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PPL_I (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate IntPtr _JniMarshal_PPL_L (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate void _JniMarshal_PPL_V (IntPtr jnienv, IntPtr klass, IntPtr p0);
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate bool _JniMarshal_PPL_Z (IntPtr jnienv, IntPtr klass, IntPtr p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tests/generator-Tests/expected.xaji/java.lang.Enum/__NamespaceMapping__.cs b/tests/generator-Tests/expected.xaji/java.lang.Enum/__NamespaceMapping__.cs
index de0f73f2d..8398c7891 100644
--- a/tests/generator-Tests/expected.xaji/java.lang.Enum/__NamespaceMapping__.cs
+++ b/tests/generator-Tests/expected.xaji/java.lang.Enum/__NamespaceMapping__.cs
@@ -2,6 +2,7 @@
 
 [assembly:global::Android.Runtime.NamespaceMapping (Java = "java.lang", Managed="Java.Lang")]
 
+[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]
 delegate int _JniMarshal_PPL_I (IntPtr jnienv, IntPtr klass, IntPtr p0);
 #if !NET
 namespace System.Runtime.Versioning {
diff --git a/tools/generator/Java.Interop.Tools.Generator.ObjectModel/NamespaceMapping.cs b/tools/generator/Java.Interop.Tools.Generator.ObjectModel/NamespaceMapping.cs
index 1c0672e8e..a8a9cd5e4 100644
--- a/tools/generator/Java.Interop.Tools.Generator.ObjectModel/NamespaceMapping.cs
+++ b/tools/generator/Java.Interop.Tools.Generator.ObjectModel/NamespaceMapping.cs
@@ -31,9 +31,12 @@ public void Generate (CodeGenerationOptions opt, GenerationInfo gen_info)
 					sw.WriteLine ();
 				}
 
+				// [UnmanagedFunctionPointer (CallingConvention.Winapi)]
 				// delegate bool _JniMarshal_PPL_Z (IntPtr jnienv, IntPtr klass, IntPtr a);
-				foreach (var jni in opt.GetJniMarshalDelegates ())
+				foreach (var jni in opt.GetJniMarshalDelegates ()) {
+					sw.WriteLine ("[global::System.Runtime.InteropServices.UnmanagedFunctionPointer (global::System.Runtime.InteropServices.CallingConvention.Winapi)]");
 					sw.WriteLine ($"delegate {FromJniType (jni[jni.Length - 1])} {jni} (IntPtr jnienv, IntPtr klass{GetDelegateParameters (jni)});");
+				}
 
 				// [SupportedOSPlatform] only exists in .NET 5.0+, so we need to generate a
 				// dummy one so earlier frameworks can compile.