diff --git a/config-linuxmodule.h.in b/config-linuxmodule.h.in
index cd88e4f89b..e9d1e53008 100644
--- a/config-linuxmodule.h.in
+++ b/config-linuxmodule.h.in
@@ -178,6 +178,9 @@
 /* Define to 1 if Linux defines the type 'uintptr_t'. */
 #undef HAVE_UINTPTR_T_LINUXMODULE
 
+/* Define to 1 to enable poisoning of freed HashAllocator blocks. */
+#undef HAVE_HASH_ALLOCATOR_POISONING
+
 /* The size of a `click_jiffies_t', as computed by sizeof. */
 #define SIZEOF_CLICK_JIFFIES_T SIZEOF_LONG
 
diff --git a/config-userlevel.h.in b/config-userlevel.h.in
index 1518766be9..48ec5c2595 100644
--- a/config-userlevel.h.in
+++ b/config-userlevel.h.in
@@ -223,6 +223,9 @@
 /* Define if you have the <valgrind/memcheck.h> header file. */
 #undef HAVE_VALGRIND_MEMCHECK_H
 
+/* Define to 1 to enable poisoning of freed HashAllocator blocks. */
+#undef HAVE_HASH_ALLOCATOR_POISONING
+
 /* Define if you have the vsnprintf function. */
 #undef HAVE_VSNPRINTF
 
diff --git a/configure.in b/configure.in
index 6360e50aa3..0047a0fe54 100644
--- a/configure.in
+++ b/configure.in
@@ -1120,6 +1120,11 @@ if test "$value" != 0; then
     AC_DEFINE_UNQUOTED([CLICK_DEBUG_SCHEDULING], [$value], [Define to enable debugging support for Click scheduling.])
 fi
 
+AC_ARG_ENABLE(hash-allocator-poisoning, [  --enable-hash-allocator-poisoning      enable HashAllocator block poisoning], :, enable_hash_allocator_poisoning=no)
+if test $enable_hash_allocator_poisoning = yes; then
+    AC_DEFINE(HAVE_HASH_ALLOCATOR_POISONING)
+fi
+
 
 dnl use Intel-specific machine instructions
 
diff --git a/include/click/hashallocator.hh b/include/click/hashallocator.hh
index 38d55cef04..8d8d88c630 100644
--- a/include/click/hashallocator.hh
+++ b/include/click/hashallocator.hh
@@ -23,6 +23,11 @@ class HashAllocator { public:
 
   private:
 
+#if HAVE_HASH_ALLOCATOR_POISONING
+    // Freed blocks are poisoned with this byte value.
+    static const uint8_t poison_byte = 0x0d;
+#endif
+
     struct link {
 	link *next;
     };
@@ -91,6 +96,9 @@ inline void *HashAllocator::allocate()
 inline void HashAllocator::deallocate(void *p)
 {
     if (p) {
+#if HAVE_HASH_ALLOCATOR_POISONING
+	memset(p, poison_byte, _size);
+#endif
 	reinterpret_cast<link *>(p)->next = _free;
 	_free = reinterpret_cast<link *>(p);
 #ifdef VALGRIND_MEMPOOL_FREE