diff --git a/mps/code/pool.c b/mps/code/pool.c
index bbdacc68616..ce7fe6d4b24 100644
--- a/mps/code/pool.c
+++ b/mps/code/pool.c
@@ -321,6 +321,7 @@ void PoolFree(Pool pool, Addr old, Size size)
   AVER(old != NULL);
   /* The pool methods should check that old is in pool. */
   AVER(size > 0);
+  AVER(AddrIsAligned(old, pool->alignment));
   AVER(PoolHasRange(pool, old, AddrAdd(old, size)));
 
   (*pool->class->free)(pool, old, size);
diff --git a/mps/test/argerr/29.c b/mps/test/argerr/29.c
index 27418458aa2..d453b65c61d 100644
--- a/mps/test/argerr/29.c
+++ b/mps/test/argerr/29.c
@@ -6,8 +6,8 @@ TEST_HEADER
  link = testlib.o
 OUTPUT_SPEC
  assert = true
- assertfile P= poolmfs.c
- assertcond = 
+ assertfile P= pool.c
+ assertcond = AddrIsAligned(old, pool->alignment)
 END_HEADER
 */