diff --git a/libobjc/ChangeLog b/libobjc/ChangeLog
index 83387eef679..56bfe2e9afb 100644
--- a/libobjc/ChangeLog
+++ b/libobjc/ChangeLog
@@ -1,3 +1,10 @@
+2010-12-21  Nicola Pero  <nicola.pero@meta-innovation.com>
+
+	* objc-private/common.h: When DEBUG is defined, include <stdio.h>.
+	Updated comments.
+	* init.c (__objc_tree_insert_class): Use %p, not %x, when printing
+	a pointer using DEBUG_PRINTF.
+	
 2010-12-21  Nicola Pero  <nicola.pero@meta-innovation.com>
 
 	PR libobjc/45953
diff --git a/libobjc/init.c b/libobjc/init.c
index 0e0d372adad..3c64f5bb7ed 100644
--- a/libobjc/init.c
+++ b/libobjc/init.c
@@ -209,7 +209,7 @@ create_tree_of_subclasses_inherited_from (Class bottom_class, Class upper)
 static objc_class_tree *
 __objc_tree_insert_class (objc_class_tree *tree, Class class)
 {
-  DEBUG_PRINTF ("__objc_tree_insert_class: tree = %x, class = %s\n",
+  DEBUG_PRINTF ("__objc_tree_insert_class: tree = %p, class = %s\n",
 		tree, class->name);
 
   if (tree == NULL)
diff --git a/libobjc/objc-private/common.h b/libobjc/objc-private/common.h
index cbb335b8f83..4f4ec5cd077 100644
--- a/libobjc/objc-private/common.h
+++ b/libobjc/objc-private/common.h
@@ -33,7 +33,14 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    being included by an external file.  */
 #define GNU_LIBOBJC_COMPILING_LIBOBJC_ITSELF 1
 
+/* When debugging libobjc, add
+
+   #define DEBUG 1
+
+   at the very beginning of a file in libobjc (before including this file) to turn
+   on DEBUG_PRINTF().  */
 #ifdef DEBUG
+#include <stdio.h>
 #define DEBUG_PRINTF(format, args...) printf (format, ## args)
 #else
 #define DEBUG_PRINTF(format, args...)