diff --git a/mdoc/Consts.cs b/mdoc/Consts.cs
index db2772edc..3ef0b9364 100644
--- a/mdoc/Consts.cs
+++ b/mdoc/Consts.cs
@@ -3,7 +3,7 @@ namespace Mono.Documentation
 {
     public static class Consts
     {
-        public static string MonoVersion = "5.8.6.1";
+        public static string MonoVersion = "5.8.7";
         public const string DocId = "DocId";
         public const string CppCli = "C++ CLI";
         public const string CppCx = "C++ CX";
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
index 37c0da244..811ff3be1 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
@@ -503,19 +503,19 @@ protected override StringBuilder AppendModifiers (StringBuilder buf, MethodDefin
         {
             string modifiers = String.Empty;
             if (method.IsStatic) modifiers += " static";
-            TypeDefinition declType = (TypeDefinition)method.DeclaringType;
-            if (declType.IsValueType && DocUtils.HasCustomAttribute(method, Consts.IsReadOnlyAttribute))
-            {
-                modifiers += " readonly";
-            }
             if (method.IsVirtual && !method.IsAbstract)
             {
                 if ((method.Attributes & MethodAttributes.NewSlot) != 0) modifiers += " virtual";
                 else modifiers += " override";
             }
+            TypeDefinition declType = (TypeDefinition)method.DeclaringType;
             if (method.IsAbstract && !declType.IsInterface) modifiers += " abstract";
             if (method.IsFinal) modifiers += " sealed";
             if (modifiers == " virtual sealed") modifiers = "";
+            if (declType.IsValueType && DocUtils.HasCustomAttribute(method, Consts.IsReadOnlyAttribute))
+            {
+                modifiers += buf.Length == 0 ? "readonly" : " readonly";
+            }
 
             switch (method.Name)
             {
@@ -593,13 +593,18 @@ private StringBuilder AppendParameter (StringBuilder buf, ParameterDefinition pa
         {
             TypeReference parameterType = parameter.ParameterType;
 
+            if (parameterType is RequiredModifierType requiredModifierType)
+            {
+                parameterType = requiredModifierType.ElementType;
+            }
+
             if (parameterType is ByReferenceType byReferenceType)
             {
                 if (parameter.IsOut)
                 {
                     buf.Append ("out ");
                 }
-                else if(parameter.IsIn)
+                else if(parameter.IsIn && DocUtils.HasCustomAttribute(parameter, Consts.IsReadOnlyAttribute))
                 {
                     buf.Append("in ");
                 }
diff --git a/mdoc/mdoc.Test/FormatterTests.cs b/mdoc/mdoc.Test/FormatterTests.cs
index 2e16f65ff..ce1009fed 100644
--- a/mdoc/mdoc.Test/FormatterTests.cs
+++ b/mdoc/mdoc.Test/FormatterTests.cs
@@ -259,9 +259,11 @@ public void FuncParams()
         [TestCase(typeof(ReadonlyRefClass), "Ref", "public ref int Ref ();")]
         [TestCase(typeof(ReadonlyRefClass), "ReadonlyRef", "public ref readonly int ReadonlyRef ();")]
         [TestCase(typeof(ReadonlyRefClass), "RefInAndOutMethod", "public void RefInAndOutMethod (ref int a, in int b, out int c);")]
+        [TestCase(typeof(ReadonlyRefClass), "InAttributeMethod", "public void InAttributeMethod (ref int a, in int b, out int c);")]
         [TestCase(typeof(GenericRefClass<>), "Ref", "public ref T Ref ();")]
         [TestCase(typeof(GenericRefClass<>), "ReadonlyRef", "public ref readonly T ReadonlyRef ();")]
         [TestCase(typeof(GenericRefClass<>), "RefInAndOutMethod", "public void RefInAndOutMethod (ref T a, in T b, out T c);")]
+        [TestCase(typeof(GenericRefClass<>), "InAttributeMethod", "public void InAttributeMethod (ref T a, in T b, out T c);")]
         public void CSharpRefReturnMethodTest(Type type, string methodName, string expectedSignature)
         {
             var member = GetMethod(type, m => m.Name == methodName);
@@ -409,12 +411,13 @@ public void CSharpReadOnlyRefStructTest()
             Assert.AreEqual("public readonly ref struct ReadOnlyRefStruct", typeSignature);
         }
 
-        [Test]
-        public void CSharpReadOnlyMemberStructTest()
+        [TestCase("Sum", "public readonly double Sum ();")]
+        [TestCase("GetNum", "readonly int Struct_Interface_A.GetNum ();")]
+        public void CSharpReadOnlyMemberStructTest(string methodName, string expectedSignature)
         {
-            var method = GetMethod(typeof(SampleClasses.StructWithReadOnlyMethod), m => m.Name == "Sum");
+            var method = GetMethod(typeof(SampleClasses.StructWithReadOnlyMethod), m => m.Name.Contains(methodName));
             var methodSignature = formatter.GetDeclaration(method);
-            Assert.AreEqual("public readonly double Sum ();", methodSignature);
+            Assert.AreEqual(expectedSignature, methodSignature);
         }
 
         #region Helper Methods
diff --git a/mdoc/mdoc.Test/SampleClasses/ReadonlyRefClass.cs b/mdoc/mdoc.Test/SampleClasses/ReadonlyRefClass.cs
index 59f356728..2ff9d09ad 100644
--- a/mdoc/mdoc.Test/SampleClasses/ReadonlyRefClass.cs
+++ b/mdoc/mdoc.Test/SampleClasses/ReadonlyRefClass.cs
@@ -1,4 +1,6 @@
-namespace mdoc.Test.SampleClasses
+using System.Runtime.InteropServices;
+
+namespace mdoc.Test.SampleClasses
 {
     public class ReadonlyRefClass
     {
@@ -12,6 +14,8 @@ public class ReadonlyRefClass
         public ref readonly int this[int index] => throw null;
 
         public void RefInAndOutMethod(ref int a, in int b, out int c) => throw null;
+
+        public void InAttributeMethod([In] ref int a, [In] in int b, [Out] out int c) => throw null;
     }
 
     public class GenericRefClass<T>
@@ -25,5 +29,7 @@ public class GenericRefClass<T>
         public ref readonly T this[int index] => throw null;
 
         public void RefInAndOutMethod(ref T a, in T b, out T c) => throw null;
+
+        public void InAttributeMethod([In] ref T a, [In] in T b, [Out] out T c) => throw null;
     }
 }
diff --git a/mdoc/mdoc.Test/SampleClasses/StructWithReadOnlyMethod.cs b/mdoc/mdoc.Test/SampleClasses/StructWithReadOnlyMethod.cs
index baf8f7af7..b61b2811b 100644
--- a/mdoc/mdoc.Test/SampleClasses/StructWithReadOnlyMethod.cs
+++ b/mdoc/mdoc.Test/SampleClasses/StructWithReadOnlyMethod.cs
@@ -1,6 +1,6 @@
 namespace mdoc.Test.SampleClasses
 {
-    public struct StructWithReadOnlyMethod
+    public struct StructWithReadOnlyMethod : Struct_Interface_A
     {
         public double X { get; set; }
         public double Y { get; set; }
@@ -9,5 +9,7 @@ public readonly double Sum()
         {
             return X + Y;
         }
+
+        readonly int Struct_Interface_A.GetNum() => 1;
     }
 }
diff --git a/mdoc/mdoc.Test/SampleClasses/Struct_Interface_A.cs b/mdoc/mdoc.Test/SampleClasses/Struct_Interface_A.cs
new file mode 100644
index 000000000..0529e0265
--- /dev/null
+++ b/mdoc/mdoc.Test/SampleClasses/Struct_Interface_A.cs
@@ -0,0 +1,7 @@
+namespace mdoc.Test.SampleClasses
+{
+    public interface Struct_Interface_A
+    {
+        int GetNum();
+    }
+}
diff --git a/mdoc/mdoc.nuspec b/mdoc/mdoc.nuspec
index 0bf49a818..6483827a7 100644
--- a/mdoc/mdoc.nuspec
+++ b/mdoc/mdoc.nuspec
@@ -2,12 +2,12 @@
 <package >
   <metadata>
     <id>mdoc</id>
-    <version>5.8.6.1</version>
+    <version>5.8.7</version>
     <title>mdoc</title>
     <authors>Microsoft</authors>
     <owners>Microsoft</owners>
     <projectUrl>https://github.com/mono/api-doc-tools</projectUrl>
-    <licenseUrl>https://github.com/mono/api-doc-tools/blob/main/LICENSE.md</licenseUrl>
+    <license type="expression">MIT</license>
     <requireLicenseAcceptance>true</requireLicenseAcceptance>
     <description>.NET API Documentation toolchain</description>
     <copyright>© Microsoft Corporation. All rights reserved.</copyright>