diff --git a/Headers/gnustep/base/Collecting.h b/Headers/gnustep/base/Collecting.h
index 0c723ddc7..e361d5824 100644
--- a/Headers/gnustep/base/Collecting.h
+++ b/Headers/gnustep/base/Collecting.h
@@ -39,7 +39,7 @@
 #include <objects/Invoking.h>
 #include <objects/Enumerating.h>
 
-@protocol ConstantCollecting
+@protocol ConstantCollecting <NSObject>
 
 // INITIALIZING;
 - init;
diff --git a/Source/objects/Collecting.h b/Source/objects/Collecting.h
index 0c723ddc7..e361d5824 100644
--- a/Source/objects/Collecting.h
+++ b/Source/objects/Collecting.h
@@ -39,7 +39,7 @@
 #include <objects/Invoking.h>
 #include <objects/Enumerating.h>
 
-@protocol ConstantCollecting
+@protocol ConstantCollecting <NSObject>
 
 // INITIALIZING;
 - init;