diff --git a/psi/zfile.c b/psi/zfile.c
index 05b8203..ee40a75 100644
--- a/psi/zfile.c
+++ b/psi/zfile.c
@@ -437,7 +437,7 @@ file_continue(i_ctx_t *i_ctx_p)
         if (code == ~(uint) 0) {    /* all done */
             esp -= 5;               /* pop proc, pfen, devlen, iodev , mark */
             return o_pop_estack;
-        } else if (code > len) {      /* overran string */
+        } else if (code > len - devlen) {      /* overran string */
             return_error(gs_error_rangecheck);
         }
         else if (iodev != iodev_default(imemory)