diff --git a/Source/PrivateHeaders/Ably/ARTRealtimeChannel+Private.h b/Source/PrivateHeaders/Ably/ARTRealtimeChannel+Private.h
index 03dbbc572..cecb367e3 100644
--- a/Source/PrivateHeaders/Ably/ARTRealtimeChannel+Private.h
+++ b/Source/PrivateHeaders/Ably/ARTRealtimeChannel+Private.h
@@ -96,10 +96,4 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-@interface ARTChannelProperties ()
-
-- (instancetype)initWithAttachSerial:(nullable NSString *)attachSerial channelSerial:(nullable NSString *)channelSerial;
-
-@end
-
 NS_ASSUME_NONNULL_END
diff --git a/Source/include/Ably/ARTRealtimeChannel.h b/Source/include/Ably/ARTRealtimeChannel.h
index b19efa083..804aa71e2 100644
--- a/Source/include/Ably/ARTRealtimeChannel.h
+++ b/Source/include/Ably/ARTRealtimeChannel.h
@@ -168,6 +168,9 @@ ART_EMBED_INTERFACE_EVENT_EMITTER(ARTChannelEvent, ARTChannelStateChange *)
  */
 @property (nonatomic, readonly, nullable) NSString *channelSerial; // CP2b
 
+// Exposed for mocking/testing purposes in conjuction with `ARTRealtimeChannelProtocol`.
+- (instancetype)initWithAttachSerial:(nullable NSString *)attachSerial channelSerial:(nullable NSString *)channelSerial;
+
 @end
 
 /**