diff --git a/src/System.Private.CoreLib/shared/System/Char.cs b/src/System.Private.CoreLib/shared/System/Char.cs
index 3835f8e99600..f69c63192c40 100644
--- a/src/System.Private.CoreLib/shared/System/Char.cs
+++ b/src/System.Private.CoreLib/shared/System/Char.cs
@@ -38,7 +38,7 @@ namespace System
         public const char MinValue = (char)0x00;
 
         // Unicode category values from Unicode U+0000 ~ U+00FF. Store them in byte[] array to save space.
-        private static ReadOnlySpan<byte> CategoryForLatin1 => new byte[] { // uses C# compiler's optimization for static byte[] data
+        private static ReadOnlySpan<byte> CategoryForLatin1 => new byte[256] { // uses C# compiler's optimization for static byte[] data
             (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0000 - 0007
             (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0008 - 000F
             (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0010 - 0017
@@ -89,7 +89,7 @@ private static bool IsAscii(char ch)
         private static UnicodeCategory GetLatin1UnicodeCategory(char ch)
         {
             Debug.Assert(IsLatin1(ch), "char.GetLatin1UnicodeCategory(): ch should be <= 007f");
-            return (UnicodeCategory)CategoryForLatin1[(int)ch];
+            return (UnicodeCategory)CategoryForLatin1[(byte)ch];
         }
 
         //
diff --git a/src/jit/rangecheck.cpp b/src/jit/rangecheck.cpp
index 96fcaf9561ec..a307e04163c3 100644
--- a/src/jit/rangecheck.cpp
+++ b/src/jit/rangecheck.cpp
@@ -1050,6 +1050,16 @@ bool RangeCheck::ComputeDoesOverflow(BasicBlock* block, GenTree* expr)
     {
         overflows = DoesPhiOverflow(block, expr);
     }
+    else if (expr->OperGet() == GT_CAST)
+    {
+        GenTreeCast* castExpr = expr->AsCast();
+        if ((castExpr->CastToType() == TYP_UBYTE || castExpr->CastToType() == TYP_USHORT) &&
+            (castExpr->CastFromType() == TYP_INT))
+        {
+            overflows = false;
+        }
+    }
+
     GetOverflowMap()->Set(expr, overflows, OverflowMap::Overwrite);
     m_pSearchPath->Remove(expr);
     return overflows;
@@ -1144,9 +1154,11 @@ Range RangeCheck::ComputeRange(BasicBlock* block, GenTree* expr, bool monotonic
             JITDUMP("%s\n", range.ToString(m_pCompiler->getAllocatorDebugOnly()));
         }
     }
-    else if (varTypeIsSmallInt(expr->TypeGet()))
+    else if (expr->OperIs(GT_CAST) || varTypeIsSmallInt(expr->TypeGet()))
     {
-        switch (expr->TypeGet())
+        var_types exprType = expr->OperIs(GT_CAST) ? expr->AsCast()->CastToType() : expr->TypeGet();
+
+        switch (exprType)
         {
             case TYP_UBYTE:
                 range = Range(Limit(Limit::keConstant, 0), Limit(Limit::keConstant, 255));