diff --git a/src/ChangeLog b/src/ChangeLog
index ffb8dd76366..d4f654a1028 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,10 @@
 2011-08-23  Eli Zaretskii  <eliz@gnu.org>
 
+	* dispnew.c (buffer_posn_from_coords): Use buf_charpos_to_bytepos
+	instead of CHAR_TO_BYTE.  Fixes a crash when a completion
+	candidate is selected by the mouse, and that candidate has a
+	composed character under the mouse.
+
 	* xdisp.c (x_produce_glyphs): Set it->nglyphs to 1.  Fixes pixel
 	coordinates reported by pos-visible-in-window-p for a composed
 	character in column zero.
diff --git a/src/dispnew.c b/src/dispnew.c
index fadfbb26603..e2bcf5d7090 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -5307,7 +5307,8 @@ buffer_posn_from_coords (struct window *w, int *x, int *y, struct display_pos *p
       if (STRINGP (it.string))
 	BYTEPOS (pos->pos) = string_char_to_byte (string, CHARPOS (pos->pos));
       else
-	BYTEPOS (pos->pos) = CHAR_TO_BYTE (CHARPOS (pos->pos));
+	BYTEPOS (pos->pos) = buf_charpos_to_bytepos (XBUFFER (w->buffer),
+						     CHARPOS (pos->pos));
     }
 
 #ifdef HAVE_WINDOW_SYSTEM