1 files changed, 2 insertions, 2 deletions

diff --git a/src/fns.c b/src/fns.c
index 0fdca30084e..2c458ba1766 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -591,7 +591,7 @@ concat (nargs, args, target_type, last_special)
                   wrong_type_argument (Qcharacterp, ch);
                 this_len_byte = CHAR_BYTES (XINT (ch));
                 result_len_byte += this_len_byte;
-                if (! ASCII_CHAR_P (XINT (ch)))
+                if (! ASCII_CHAR_P (XINT (ch)) && ! CHAR_BYTE8_P (XINT (ch)))
                   some_multibyte = 1;
               }
           else if (BOOL_VECTOR_P (this) && XBOOL_VECTOR (this)->size > 0)
@@ -604,7 +604,7 @@ concat (nargs, args, target_type, last_special)
                   wrong_type_argument (Qcharacterp, ch);
                 this_len_byte = CHAR_BYTES (XINT (ch));
                 result_len_byte += this_len_byte;
-                if (! ASCII_CHAR_P (XINT (ch)))
+                if (! ASCII_CHAR_P (XINT (ch)) && ! CHAR_BYTE8_P (XINT (ch)))
                   some_multibyte = 1;
               }
           else if (STRINGP (this))