1 files changed, 22 insertions, 1 deletions

diff --git a/src/fileio.c b/src/fileio.c
index e444b1474d2..e3ca6cd4e2a 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -3698,7 +3698,14 @@ actually used.")
 
           /* We win!  We can handle REPLACE the optimized way.  */
 
-          /* Extends the end of non-matching text area to multibyte
+          /* Extend the start of non-matching text area to multibyte
+             character boundary.  */
+          if (! NILP (current_buffer->enable_multibyte_characters))
+            while (same_at_start > BEGV_BYTE
+                   && ! CHAR_HEAD_P (FETCH_BYTE (same_at_start)))
+              same_at_start--;
+
+          /* Extend the end of non-matching text area to multibyte
              character boundary.  */
           if (! NILP (current_buffer->enable_multibyte_characters))
             while (same_at_end < ZV_BYTE
@@ -3853,6 +3860,13 @@ actually used.")
           goto handled;
         }
 
+      /* Extend the start of non-matching text area to multibyte
+         character boundary.  */
+      if (! NILP (current_buffer->enable_multibyte_characters))
+        while (same_at_start > BEGV_BYTE
+               && ! CHAR_HEAD_P (FETCH_BYTE (same_at_start)))
+          same_at_start--;
+
       /* Scan this bufferful from the end, comparing with
          the Emacs buffer.  */
       bufpos = inserted;
@@ -3863,6 +3877,13 @@ actually used.")
              && FETCH_BYTE (same_at_end - 1) == conversion_buffer[bufpos - 1])
         same_at_end--, bufpos--;
 
+      /* Extend the end of non-matching text area to multibyte
+         character boundary.  */
+      if (! NILP (current_buffer->enable_multibyte_characters))
+        while (same_at_end < ZV_BYTE
+               && ! CHAR_HEAD_P (FETCH_BYTE (same_at_end)))
+          same_at_end++;
+
       /* Don't try to reuse the same piece of text twice.  */
       overlap = same_at_start - BEGV_BYTE - (same_at_end + inserted - ZV_BYTE);
       if (overlap > 0)