diff --git a/CSharp.Ulid/Ulid.cs b/CSharp.Ulid/Ulid.cs
index 3f339c7..741bb25 100644
--- a/CSharp.Ulid/Ulid.cs
+++ b/CSharp.Ulid/Ulid.cs
@@ -146,6 +146,7 @@ private static void AddOne(byte[] bytes)
 
                 bytes[index] = 0;
             }
+            throw new Exception("No more randomness available. Too many IDs generated this millisecond.");
         }
 
         public override string ToString() => StringExtensions.Create(VALID_ULID_STRING_LENGTH, new UlidStringHelper(this), (buffer, value) =>