diff --git a/common/ChangeLog b/common/ChangeLog
index 6a6f6e071..fe9eb4fc0 100644
--- a/common/ChangeLog
+++ b/common/ChangeLog
@@ -1,3 +1,7 @@
+2011-01-18  Werner Koch  <wk@g10code.com>
+
+	* estream.c (es_func_mem_write): FIX computation of NEWSIZE.
+
 2011-01-10  Werner Koch  <wk@g10code.com>
 
 	* session-env.c (update_var): Fix same value detection.  Fixes
diff --git a/common/estream.c b/common/estream.c
index bc25452ed..416aa8376 100644
--- a/common/estream.c
+++ b/common/estream.c
@@ -641,7 +641,7 @@ es_func_mem_write (void *cookie, const void *buffer, size_t size)
       if (!mem_cookie->memory_size)
         newsize = size;  /* Not yet allocated.  */
       else
-        newsize = mem_cookie->memory_size + (nleft - size);
+        newsize = mem_cookie->memory_size + (size - nleft);
       if (newsize < mem_cookie->offset)
         {
           _set_errno (EINVAL);