diff --git a/libguile/ports.c b/libguile/ports.c
index 4081183bc..1f9a50fe9 100644
--- a/libguile/ports.c
+++ b/libguile/ports.c
@@ -216,7 +216,7 @@ SCM
 scm_char_ready_p (port)
      SCM port;
 {
-  scm_port *pt = SCM_PTAB_ENTRY (port);
+  scm_port *pt;
 
   if (SCM_UNBNDP (port))
     port = scm_cur_inp;
@@ -224,6 +224,8 @@ scm_char_ready_p (port)
     SCM_ASSERT (SCM_NIMP (port) && SCM_OPINPORTP (port), port, SCM_ARG1,
 		s_char_ready_p);
 
+  pt = SCM_PTAB_ENTRY (port);
+
   /* if the current read buffer is filled, or the
      last pushed-back char has been read and the saved buffer is
      filled, result is true.  */