diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index d9f1c99..1cf090c 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -2094,12 +2094,17 @@
     /*
      * Write to another file or b_flags set or not writing the whole file:
      * overwriting only allowed with '!'.
+     * If "other" is FALSE and bt_nofilename(buf) is TRUE, this must be
+     * writing an "acwrite" buffer to the same file as its b_ffname, and
+     * buf_write() will only allow writing with BufWriteCmd autocommands,
+     * so there is no need for an overwrite check.
      */
     if (       (other
-		|| (buf->b_flags & BF_NOTEDITED)
-		|| ((buf->b_flags & BF_NEW)
-		    && vim_strchr(p_cpo, CPO_OVERNEW) == NULL)
-		|| (buf->b_flags & BF_READERR))
+		|| (!bt_nofilename(buf)
+		    && ((buf->b_flags & BF_NOTEDITED)
+			|| ((buf->b_flags & BF_NEW)
+			    && vim_strchr(p_cpo, CPO_OVERNEW) == NULL)
+			|| (buf->b_flags & BF_READERR))))
 	    && !p_wa
 	    && vim_fexists(ffname))
     {