diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index 43009b35b2a..7eb136af5f1 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -678,10 +678,11 @@ Initialize the process query flag to @var{query-flag}.
 @xref{Query Before Exit}.
 
 @item :stop @var{stopped}
-@var{stopped} must be @code{nil}.  The @code{:stop} key is ignored
-otherwise and is retained for compatibility with other process types
-such as pipe processes.  Asynchronous subprocesses never start in the
-stopped state.
+If provided, @var{stopped} must be @code{nil}; it is an error to use
+any non-@code{nil} value.  The @code{:stop} key is ignored otherwise
+and is retained for compatibility with other process types such as
+pipe processes.  Asynchronous subprocesses never start in the stopped
+state.
 
 @item :filter @var{filter}
 Initialize the process filter to @var{filter}.  If not specified, a