diff --git a/layout/base/nsPresArena.cpp b/layout/base/nsPresArena.cpp
index 7494dad4608..5cc33b3c403 100644
--- a/layout/base/nsPresArena.cpp
+++ b/layout/base/nsPresArena.cpp
@@ -83,11 +83,7 @@
 #endif
 
 // Size to use for PLArena block allocations.
-// XXX: This should be 8192;  the subtracted elements are a hack that's
-// required to ensure the allocation requests are power-of-two-sized and thus
-// avoid lots of wasted memory caused by the heap allocator rounding up request
-// sizes.  Bug 676457 will fix it properly.
-static const size_t ARENA_PAGE_SIZE = 8192 - sizeof(PLArena) - PL_ARENA_CONST_ALIGN_MASK;
+static const size_t ARENA_PAGE_SIZE = 8192;
 
 // Freed memory is filled with a poison value, which we arrange to
 // form a pointer either to an always-unmapped region of the address