diff --git a/ChangeLog b/ChangeLog
index 17f6538c..53d9caf8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -16,6 +16,10 @@ brevity.  Much more detail can be found in the git revision history:
   - Add JEMALLOC_CXX_THROW to the memalign() function prototype, in order to
     match glibc and avoid compilation errors when including both
     jemalloc/jemalloc.h and malloc.h in C++ code.
+  - Fix chunk purge hook calls for in-place huge shrinking reallocation to
+    specify the old chunk size rather than the new chunk size.  This bug caused
+    no correctness issues for the default chunk purge function, but was
+    visible to custom functions set via the "arena.<i>.chunk_hooks" mallctl.
 
 * 4.0.0 (August 17, 2015)
 
diff --git a/src/huge.c b/src/huge.c
index 54c2114c..f49a9376 100644
--- a/src/huge.c
+++ b/src/huge.c
@@ -149,7 +149,7 @@ huge_ralloc_no_move_similar(void *ptr, size_t oldsize, size_t usize,
 	if (oldsize > usize) {
 		size_t sdiff = oldsize - usize;
 		zeroed = !chunk_purge_wrapper(arena, &chunk_hooks, ptr,
-		    CHUNK_CEILING(usize), usize, sdiff);
+		    CHUNK_CEILING(oldsize), usize, sdiff);
 		if (config_fill && unlikely(opt_junk_free)) {
 			memset((void *)((uintptr_t)ptr + usize), 0x5a, sdiff);
 			zeroed = false;
@@ -204,7 +204,7 @@ huge_ralloc_no_move_shrink(void *ptr, size_t oldsize, size_t usize)
 		size_t sdiff = oldsize - usize;
 		zeroed = !chunk_purge_wrapper(arena, &chunk_hooks,
 		    CHUNK_ADDR2BASE((uintptr_t)ptr + usize),
-		    CHUNK_CEILING(usize), CHUNK_ADDR2OFFSET((uintptr_t)ptr +
+		    CHUNK_CEILING(oldsize), CHUNK_ADDR2OFFSET((uintptr_t)ptr +
 		    usize), sdiff);
 		if (config_fill && unlikely(opt_junk_free)) {
 			huge_dalloc_junk((void *)((uintptr_t)ptr + usize),