diff --git a/src/libraries/System.Net.Security/src/System/Net/NegotiateAuthenticationPal.ManagedNtlm.cs b/src/libraries/System.Net.Security/src/System/Net/NegotiateAuthenticationPal.ManagedNtlm.cs
index 147097e521c700..df2ffee5fe2910 100644
--- a/src/libraries/System.Net.Security/src/System/Net/NegotiateAuthenticationPal.ManagedNtlm.cs
+++ b/src/libraries/System.Net.Security/src/System/Net/NegotiateAuthenticationPal.ManagedNtlm.cs
@@ -333,7 +333,7 @@ private static ReadOnlySpan<byte> GetField(MessageField field, ReadOnlySpan<byte
 
             private static unsafe void SetField(ref MessageField field, int length, int offset)
             {
-                if (length > short.MaxValue)
+                if (length is < 0 or > short.MaxValue)
                 {
                     throw new Win32Exception(NTE_FAIL);
                 }