diff --git a/README.md b/README.md
index b22c0da4..b3826106 100644
--- a/README.md
+++ b/README.md
@@ -152,7 +152,7 @@ public interface Subscriber<T> {
 | <a name="2.11">11</a>     | A `Subscriber` MUST make sure that all calls on its [signal](#term_signal) methods happen-before the processing of the respective signals. I.e. the Subscriber must take care of properly publishing the signal to its processing logic. |
 | [:bulb:](#2.11 "2.11 explained") | *The intent of this rule is to establish that it is the responsibility of the Subscriber implementation to make sure that asynchronous processing of its signals are thread safe. See [JMM definition of Happens-Before in section 17.4.5](https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html#jls-17.4.5).* |
 | <a name="2.12">12</a>     | `Subscriber.onSubscribe` MUST be called at most once for a given `Subscriber` (based on object equality). |
-| [:bulb:](#2.12 "2.12 explained") | *The intent of this rule is to establish that it MUST be assumed that the same Subscriber can only be subscribed at most once.* |
+| [:bulb:](#2.12 "2.12 explained") | *The intent of this rule is to establish that it MUST be assumed that the same Subscriber can only be subscribed at most once. Note that `object equality` is `a.equals(b)`.* |
 | <a name="2.13">13</a>     | Calling `onSubscribe`, `onNext`, `onError` or `onComplete` MUST [return normally](#term_return_normally) except when any provided parameter is `null` in which case it MUST throw a `java.lang.NullPointerException` to the caller, for all other situations the only legal way for a `Subscriber` to signal failure is by cancelling its `Subscription`. In the case that this rule is violated, any associated `Subscription` to the `Subscriber` MUST be considered as cancelled, and the caller MUST raise this error condition in a fashion that is adequate for the runtime environment. |
 | [:bulb:](#2.13 "2.13 explained") | *The intent of this rule is to establish the semantics for the methods of Subscriber and what the Publisher is allowed to do in which case this rule is violated. «Raise this error condition in a fashion that is adequate for the runtime environment» could mean logging the error—or otherwise make someone or something aware of the situation—as the error cannot be signalled to the faulty Subscriber.* |