diff --git a/include/libtorrent/allocator.hpp b/include/libtorrent/allocator.hpp
index fd44d0006..31060a225 100644
--- a/include/libtorrent/allocator.hpp
+++ b/include/libtorrent/allocator.hpp
@@ -47,7 +47,7 @@ namespace libtorrent
 		typedef std::ptrdiff_t difference_type;
 
 		static char* malloc(const size_type bytes);
-		static void free(char* const block);
+		static void free(char* block);
 	};
 
 	struct TORRENT_EXTRA_EXPORT aligned_holder
diff --git a/src/allocator.cpp b/src/allocator.cpp
index 36142b22a..f1c205beb 100644
--- a/src/allocator.cpp
+++ b/src/allocator.cpp
@@ -97,21 +97,45 @@ namespace libtorrent
 
 	char* page_aligned_allocator::malloc(size_type bytes)
 	{
+		TORRENT_ASSERT(bytes > 0);
+		// just sanity check (this needs to be pretty high
+		// for cases where the cache size is several gigabytes)
+		TORRENT_ASSERT(bytes < 0x30000000);
+
 		TORRENT_ASSERT(bytes >= page_size());
 #ifdef TORRENT_DEBUG_BUFFERS
 		int page = page_size();
 		int num_pages = (bytes + (page-1)) / page + 2;
-		char* ret = (char*)valloc(num_pages * page);
-		// make the two surrounding pages non-readable and -writable
-		alloc_header* h = (alloc_header*)ret;
-		h->size = bytes;
-		h->magic = 0x1337;
-#if defined __linux__ || (defined __APPLE__ && MAC_OS_X_VERSION_MIN_REQUIRED >= 1050)
-		print_backtrace(h->stack, sizeof(h->stack));
+		int orig_bytes = bytes;
+		bytes = num_pages * page;
 #endif
 
+		char* ret;
+#if TORRENT_USE_POSIX_MEMALIGN
+		if (posix_memalign((void**)&ret, page_size(), bytes) != 0) ret = NULL;
+#elif TORRENT_USE_MEMALIGN
+		ret = (char*)memalign(page_size(), bytes);
+#elif defined TORRENT_WINDOWS
+		ret = (char*)_aligned_malloc(bytes, page_size());
+#elif defined TORRENT_BEOS
+		area_id id = create_area("", &ret, B_ANY_ADDRESS
+			, (bytes + page_size() - 1) & (page_size()-1), B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
+		if (id < B_OK) return NULL;
+		ret = (char*)ret;
+#else
+		ret = (char*)valloc(bytes);
+#endif
+		if (ret == NULL) return NULL;
+
+#ifdef TORRENT_DEBUG_BUFFERS
+		// make the two surrounding pages non-readable and -writable
+		alloc_header* h = (alloc_header*)ret;
+		h->size = orig_bytes;
+		h->magic = 0x1337;
+		print_backtrace(h->stack, sizeof(h->stack));
+
 #ifdef TORRENT_WINDOWS
-#define mprotect(buf, size, prot) VirtualProtect(buf, size, prot, NULK)
+#define mprotect(buf, size, prot) VirtualProtect(buf, size, prot, NULL)
 #define PROT_READ PAGE_READONLY
 #endif
 		mprotect(ret, page, PROT_READ);
@@ -124,35 +148,19 @@ namespace libtorrent
 //		fprintf(stderr, "malloc: %p head: %p tail: %p size: %d\n", ret + page, ret, ret + page + bytes, int(bytes));
 
 		return ret + page;
-#else
-
-#if TORRENT_USE_POSIX_MEMALIGN
-		void* ret;
-		if (posix_memalign(&ret, page_size(), bytes) != 0) ret = 0;
-		return (char*)ret;
-#elif TORRENT_USE_MEMALIGN
-		return (char*)memalign(page_size(), bytes);
-#elif defined TORRENT_WINDOWS
-		return (char*)_aligned_malloc(bytes, page_size());
-#elif defined TORRENT_BEOS
-		void* ret = 0;
-		area_id id = create_area("", &ret, B_ANY_ADDRESS
-			, (bytes + page_size() - 1) & (page_size()-1), B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
-		if (id < B_OK) return 0;
-		return (char*)ret;
-#else
-		return (char*)valloc(bytes);
-#endif
 #endif // TORRENT_DEBUG_BUFFERS
+
+		return ret;
 	}
 
-	void page_aligned_allocator::free(char* const block)
+	void page_aligned_allocator::free(char* block)
 	{
+		if (block == 0) return;
 
 #ifdef TORRENT_DEBUG_BUFFERS
 
 #ifdef TORRENT_WINDOWS
-#define mprotect(buf, size, prot) VirtualProtect(buf, size, prot, NULK)
+#define mprotect(buf, size, prot) VirtualProtect(buf, size, prot, NULL)
 #define PROT_READ PAGE_READONLY
 #define PROT_WRITE PAGE_READWRITE
 #endif
@@ -165,6 +173,7 @@ namespace libtorrent
 		mprotect(block + (num_pages-2) * page, page, PROT_READ | PROT_WRITE);
 //		fprintf(stderr, "free: %p head: %p tail: %p size: %d\n", block, block - page, block + h->size, int(h->size));
 		h->magic = 0;
+		block -= page;
 
 #ifdef TORRENT_WINDOWS
 #undef mprotect
@@ -175,8 +184,6 @@ namespace libtorrent
 #if defined __linux__ || (defined __APPLE__ && MAC_OS_X_VERSION_MIN_REQUIRED >= 1050)
 		print_backtrace(h->stack, sizeof(h->stack));
 #endif
-		::free(block - page);
-		return;
 #endif // TORRENT_DEBUG_BUFFERS
 
 #ifdef TORRENT_WINDOWS