diff --git a/src/mempool.c b/src/mempool.c
index 8e421d5a..74380cc5 100644
--- a/src/mempool.c
+++ b/src/mempool.c
@@ -48,11 +48,12 @@ sos_alloc (size_t size)
 #ifdef HAVE_CMPXCHG
   union {
     long *lp;
-    char *cp;
+    char **cp;
   } u;
   char *old_mem;
 
   size = (size + MAX_ALIGN - 1) & -MAX_ALIGN;
+  u.cp = &sos_memp;
   do
     {
       old_mem = sos_memp;
@@ -61,9 +62,8 @@ sos_alloc (size_t size)
       mem += size;
       if (mem >= sos_memory + sizeof (sos_memory))
 	abort ();
-      u.cp = sos_memp;
     }
-  while (!cmpxchg_ptr (&u.lp, old_mem, mem));
+  while (!cmpxchg_ptr (u.lp, old_mem, mem));
 #else
   static pthread_mutex_t sos_lock = PTHREAD_MUTEX_INITIALIZER;
   sigset_t saved_sigmask;