Index: src/OFObject.h
==================================================================
--- src/OFObject.h
+++ src/OFObject.h
@@ -414,11 +414,11 @@
 @end
 
 /**
  * \brief A protocol for the creation of copies.
  */
-@protocol OFCopying
+@protocol OFCopying <OFObject>
 /**
  * \return A copy of the object
  */
 - copy;
 @end
@@ -427,11 +427,11 @@
  * \brief A protocol for the creation of mutable copies.
  *
  * This protocol is implemented by objects that can be mutable and immutable
  * and allows returning a mutable copy.
  */
-@protocol OFMutableCopying
+@protocol OFMutableCopying <OFCopying>
 /**
  * \return A mutable copy of the object
  */
 - mutableCopy;
 @end
@@ -439,11 +439,11 @@
 /**
  * \brief A protocol for comparing objects.
  *
  * This protocol is implemented by objects that can be compared.
  */
-@protocol OFComparing
+@protocol OFComparing <OFObject>
 /**
  * Compares the object with another object.
  *
  * \param object An object to compare the object to
  * \return The result of the comparison