diff --git a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X25519DiffieHellmanCng.Windows.cs b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X25519DiffieHellmanCng.Windows.cs
index 4c36b457306c85..c02392df0f300d 100644
--- a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X25519DiffieHellmanCng.Windows.cs
+++ b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X25519DiffieHellmanCng.Windows.cs
@@ -41,7 +41,13 @@ protected override partial void DeriveRawSecretAgreementCore(X25519DiffieHellman
         {
             // We intentionally don't special case otherParty being an instance of X25519DiffieHellmanCng and always
             // export the public key into the current instance's provider.
-            Span<byte> publicKeyBuffer = stackalloc byte[PublicKeySizeInBytes * 2];
+            scoped Span<byte> publicKeyBuffer;
+
+            unsafe
+            {
+                publicKeyBuffer = stackalloc byte[PublicKeySizeInBytes * 2];
+            }
+
             Span<byte> publicKeyBytes = publicKeyBuffer.Slice(0, PublicKeySizeInBytes);
             Span<byte> reducedPublicKey = publicKeyBuffer.Slice(PublicKeySizeInBytes, PublicKeySizeInBytes);
             otherParty.ExportPublicKey(publicKeyBytes);