1 files changed, 6 insertions, 1 deletions

diff --git a/src/xselect.c b/src/xselect.c
index bf37cde4d0b..8d8efd8db8a 100644
--- a/src/xselect.c
+++ b/src/xselect.c
@@ -1908,7 +1908,12 @@ lisp_data_to_selection_data (display, obj,
     }
   else if (STRINGP (obj))
     {
-      xassert (! STRING_MULTIBYTE (obj));
+      if (SCHARS (obj) < SBYTES (obj))
+        /* OBJ is a multibyte string containing a non-ASCII char.  */
+        Fsignal (Qerror, /* Qselection_error */
+                 Fcons (build_string
+                        ("Non-ASCII string must be encoded in advance"),
+                        Fcons (obj, Qnil)));
       if (NILP (type))
         type = QSTRING;
       *format_ret = 8;