diff --git a/IDEHelper/Compiler/BfMangler.cpp b/IDEHelper/Compiler/BfMangler.cpp
index 5792fe23..257e5633 100644
--- a/IDEHelper/Compiler/BfMangler.cpp
+++ b/IDEHelper/Compiler/BfMangler.cpp
@@ -535,18 +535,16 @@ void BfGNUMangler::Mangle(MangleContext& mangleContext, StringImpl& name, BfType
 	else if (type->IsRef())
 	{
 		BfRefType* refType = (BfRefType*)type;
-		if ((refType->mRefKind == BfRefType::RefKind_Mut) && (!mangleContext.mCCompat))
+		if (refType->mRefKind == BfRefType::RefKind_In)
+		{
+			isConst = true;
+		}
+		else if ((refType->mRefKind == BfRefType::RefKind_Mut) && (!mangleContext.mCCompat))
 		{
 			name += "U3mut";
 			Mangle(mangleContext, name, refType->mElementType);
 			return;
-		}
-		else if ((refType->mRefKind == BfRefType::RefKind_In) && (!mangleContext.mCCompat))
-		{
-			name += "U2in";
-			Mangle(mangleContext, name, refType->mElementType);
-			return;
-		}
+		}		
 		else if ((refType->mRefKind == BfRefType::RefKind_Out) && (!mangleContext.mCCompat))
 		{
 			name += "U3out";
@@ -1649,14 +1647,12 @@ void BfMSMangler::Mangle(MangleContext& mangleContext, StringImpl& name, BfType*
 		name += "A";
 		if (mangleContext.mIs64Bit)
 			name += "E";
-		if (isConst)
+		if ((isConst) || (refType->mRefKind == BfRefType::RefKind_In))
 			name += "B";
 		else
 			name += "A";
 		if (refType->mRefKind == BfRefType::RefKind_Mut)
-			name += "mut$";
-		else if (refType->mRefKind == BfRefType::RefKind_In)
-			name += "in$";
+			name += "mut$";		
 		else if (refType->mRefKind == BfRefType::RefKind_Out)
 			name += "out$";
 		Mangle(mangleContext, name, refType->mElementType);
diff --git a/IDEHelper/Tests/src/Interop.bf b/IDEHelper/Tests/src/Interop.bf
index 3176ddce..141aa49b 100644
--- a/IDEHelper/Tests/src/Interop.bf
+++ b/IDEHelper/Tests/src/Interop.bf
@@ -19,6 +19,9 @@ namespace Tests
 			[LinkName(.CPP)]
 			[return: MangleConst]
 			public extern ref float MethodA2([MangleConst]ref float val);
+			[LinkName(.CPP)]
+			[return: MangleConst]
+			public extern ref float MethodA3(in float val);
 		}
 
 		[CRepr]
@@ -399,6 +402,7 @@ namespace Tests
 			Test.Assert(StructA.sVal == 1234);
 			float f = 123;
 			Test.Assert(sa0.MethodA2(ref f) == 123);
+			Test.Assert(sa0.MethodA3(f) == 123);
 
 			StartTest("Func0");
 			Test.Assert(Func0(12, 34) == 3412);