@@ -68,6 +68,12 @@ bool BoundsCheckInfo::Initialize(const Compiler* comp, Statement* statement, int
         return false;
     }
 
+    // The guards are built as TYP_INT, so native-int (e.g. nint index) bounds checks aren't supported.
+    if ((genActualType(BndChk()->GetIndex()) != TYP_INT) || (genActualType(BndChk()->GetArrayLength()) != TYP_INT))
+    {
+        return false;
+    }
+
     if (BndChk()->GetIndex()->IsIntCnsFitsInI32())
     {
         // Index being a constant means we have index=0 and cns offset
 
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class Runtime_134459
+{
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        int[] arr = new int[8];
+        Test(arr);
+        Assert.Equal(new int[] { 1, 2, 3, 4, 0, 0, 0, 0 }, arr);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+    private static void Test(int[] arr)
+    {
+        arr[(nint)0] = 1;
+        arr[(nint)1] = 2;
+        arr[(nint)2] = 3;
+        arr[(nint)3] = 4;
+    }
+}
Original file line number	Diff line number	Diff line change
`@@ -68,6 +68,12 @@ bool BoundsCheckInfo::Initialize(const Compiler* comp, Statement* statement, int`
`68`	`68`	`return false;`
`69`	`69`	`}`
`70`	`70`
	`71`	`+ // The guards are built as TYP_INT, so native-int (e.g. nint index) bounds checks aren't supported.`
	`72`	`+ if ((genActualType(BndChk()->GetIndex()) != TYP_INT) \|\| (genActualType(BndChk()->GetArrayLength()) != TYP_INT))`
	`73`	`+ {`
	`74`	`+ return false;`
	`75`	`+ }`
	`76`	`+`
`71`	`77`	`if (BndChk()->GetIndex()->IsIntCnsFitsInI32())`
`72`	`78`	`{`
`73`	`79`	`// Index being a constant means we have index=0 and cns offset`