diff --git a/src/NSubstitute/Arg.cs b/src/NSubstitute/Arg.cs
index 6d0fc49d..7cfd4000 100644
--- a/src/NSubstitute/Arg.cs
+++ b/src/NSubstitute/Arg.cs
@@ -39,18 +39,18 @@ public static ref T Is<T>(T value)
     /// Match argument that satisfies <paramref name="predicate"/>.
     /// If the <paramref name="predicate"/> throws an exception for an argument it will be treated as non-matching.
     /// </summary>
-    public static ref T Is<T>(Expression<Predicate<T?>> predicate)
+    public static ref T Is<T>(Expression<Predicate<T>> predicate)
     {
-        return ref ArgumentMatcher.Enqueue<T>(new ExpressionArgumentMatcher<T>(predicate));
+        return ref ArgumentMatcher.Enqueue<T>(new ExpressionArgumentMatcher<T>(predicate!));
     }
 
     /// <summary>
     /// Match argument that satisfies <paramref name="predicate"/>.
     /// If the <paramref name="predicate"/> throws an exception for an argument it will be treated as non-matching.
     /// </summary>
-    public static ref T Is<T>(Expression<Predicate<object?>> predicate) where T : AnyType
+    public static ref T Is<T>(Expression<Predicate<object>> predicate) where T : AnyType
     {
-        return ref ArgumentMatcher.Enqueue<T>(new ExpressionArgumentMatcher<object>(predicate));
+        return ref ArgumentMatcher.Enqueue<T>(new ExpressionArgumentMatcher<object>(predicate!));
     }
 
     /// <summary>