diff --git a/src/lsh_types.h b/src/lsh_types.h
index 1c3f0e94cda1743d62d83694c4b54876a03510dc..f74befbfd73a9accda494f244bc6d8429c0cce52 100644
--- a/src/lsh_types.h
+++ b/src/lsh_types.h
@@ -79,9 +79,27 @@ do {						\
 #define MIN(a, b) (((a)>(b)) ? (b) : (a))
 #define MAX(a, b) (((a)>(b)) ? (b) : (a))
 
-/* Generic packet */
+/* Generic object */
+
+#ifdef DEBUG_ALLOC
+
+struct lsh_object
+{
+  int type;  /* Zero for objects that are not allocated on the heap. */
+};
+
+#define STATIC_HEADER { 0 },
+
+#else   /* !DEBUG_ALLOC */
+struct lsh_object {};
+#define STATIC_HEADER
+
+#endif  /* !DEBUG_ALLOC */
+
 struct lsh_string
 {
+  struct lsh_object header;
+  
   UINT32 sequence_number; 
   UINT32 length;
   UINT8 data[1];
@@ -92,7 +110,9 @@ struct callback;
 typedef int (*callback_f)(struct callback *closure);
 struct callback
 {
-  callback_f f;
+  struct lsh_object header;
+  
+  int (*f)(struct callback *closure);
 };
 
 #define CALLBACK(c) ((c)->f(c))
diff --git a/src/randomness.h b/src/randomness.h
index 09b0e9964530f175d59efce8090693082fc3e91f..53d79add47bc7a6107723d8942cf6b948263f658 100644
--- a/src/randomness.h
+++ b/src/randomness.h
@@ -30,6 +30,8 @@
 
 struct randomness
 {
+  struct lsh_object header;
+  
   void (*random)(struct randomness **closure, UINT32 length, UINT8 *dst);
 };
 
diff --git a/src/read_line.h b/src/read_line.h
index 27b13a0b264e55bcdd1437098c4fda907eab6d99..c191dfd09a1eea06bc2636cec9735a533aee2530 100644
--- a/src/read_line.h
+++ b/src/read_line.h
@@ -34,6 +34,8 @@
 /* May store a new handler into *h. */
 struct line_handler
 {
+  struct lsh_object header;
+  
   struct read_handler * (*handler)(struct line_handler **h,
 				   UINT32 length,
 				   UINT8 *line);
diff --git a/src/write_buffer.h b/src/write_buffer.h
index 9d77fdaca23799807d44799c8468f9d4c03ec11c..519725342c695fb215d1037702de26b7e5357e32 100644
--- a/src/write_buffer.h
+++ b/src/write_buffer.h
@@ -31,6 +31,8 @@
 /* For the packet queue */
 struct node
 {
+  struct lsh_object header;
+  
   struct node *next;
   struct node *prev;
   struct lsh_string *packet;