diff --git a/HarmonyTests/Tools/TestAccessTools.cs b/HarmonyTests/Tools/TestAccessTools.cs
index 5437e72e..af3d0ffc 100644
--- a/HarmonyTests/Tools/TestAccessTools.cs
+++ b/HarmonyTests/Tools/TestAccessTools.cs
@@ -500,6 +500,44 @@ public void Test_AccessTools_MethodDelegate_OpenInstanceDelegates_InterfaceMetho
 			_ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDel<Struct>>(interfaceTest, virtualCall: false)(structInstance, 456, ref f));
 		}
 
+		[Test]
+		public void Test_AccessTools_MethodDelegate_OpenInstanceDelegates_Arg0ByRef()
+		{
+			// only applies to struct, since you want to mutate structs via ref
+			var f = 789f;
+
+			var structInstance = new Struct();
+			// repeat for mutation
+			Assert.AreEqual("struct result 456 790 1", AccessTools.MethodDelegate<OpenMethodDelRefInstance<Struct>>(structTest, virtualCall: false, delegateArgs: [typeof(Struct).MakeByRefType(), typeof(int), typeof(float).MakeByRefType()])(ref structInstance, 456, ref f));
+			Assert.AreEqual("struct result 456 791 2", AccessTools.MethodDelegate<OpenMethodDelRefInstance<Struct>>(structTest, virtualCall: false, delegateArgs: [typeof(Struct).MakeByRefType(), typeof(int), typeof(float).MakeByRefType()])(ref structInstance, 456, ref f));
+			Assert.AreEqual("struct result 456 792 3", AccessTools.MethodDelegate<OpenMethodDelRefInstance<Struct>>(structTest, virtualCall: false, delegateArgs: [typeof(Struct).MakeByRefType(), typeof(int), typeof(float).MakeByRefType()])(ref structInstance, 456, ref f));
+		}
+
+		[Test]
+		public void Test_AccessTools_MethodDelegate_OpenInstanceDelegates_BoxedArgs()
+		{
+			var f = 789f;
+			var baseInstance = new Base();
+			var derivedInstance = new Derived();
+			var structInstance = new Struct();
+			// Assert.AreEqual("base test 456 790 1", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<IInterface>>(interfaceTest, virtualCall: true)(baseInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<IInterface>>(interfaceTest, virtualCall: false)(baseInstance, 456, ref f));
+			// Assert.AreEqual("derived test 456 791 1", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<IInterface>>(interfaceTest, virtualCall: true)(derivedInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<IInterface>>(interfaceTest, virtualCall: false)(derivedInstance, 456, ref f));
+			// Assert.AreEqual("struct result 456 792 1", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<IInterface>>(interfaceTest, virtualCall: true)(structInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<IInterface>>(interfaceTest, virtualCall: false)(structInstance, 456, ref f));
+			// Assert.AreEqual("base test 456 793 2", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Base>>(interfaceTest, virtualCall: true)(baseInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Base>>(interfaceTest, virtualCall: false)(baseInstance, 456, ref f));
+			// Assert.AreEqual("derived test 456 794 2", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Base>>(interfaceTest, virtualCall: true)(derivedInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Base>>(interfaceTest, virtualCall: false)(derivedInstance, 456, ref f));
+			// // AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Derived>>(interfaceTest, virtualCall: true)(baseInstance, 456, ref f)); // expected compile error
+			// // AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Derived>>(interfaceTest, virtualCall: false)(baseInstance, 456, ref f)); // expected compile error
+			// Assert.AreEqual("derived test 456 795 3", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Derived>>(interfaceTest, virtualCall: true)(derivedInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Derived>>(interfaceTest, virtualCall: false)(derivedInstance, 456, ref f));
+			// Assert.AreEqual("struct result 456 796 1", AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Struct>>(interfaceTest, virtualCall: true)(structInstance, 456, ref f));
+			// _ = Assert.Throws(typeof(ArgumentException), () => AccessTools.MethodDelegate<OpenMethodDelBoxedArg<Struct>>(interfaceTest, virtualCall: false)(structInstance, 456, ref f));
+		}
+
 		[Test]
 		public void Test_AccessTools_MethodDelegate_StaticDelegates_InterfaceMethod()
 		{
@@ -520,6 +558,8 @@ public void Test_AccessTools_MethodDelegate_InvalidDelegates()
 
 		delegate string MethodDel(int n, ref float f);
 		delegate string OpenMethodDel<T>(T instance, int n, ref float f);
+		delegate string OpenMethodDelRefInstance<T>(ref T instance, int n, ref float f);
+		delegate string OpenMethodDelBoxedArg<T>(T instance, object n, ref float f);
 
 		[Test]
 		public void Test_AccessTools_HarmonyDelegate()