--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -2912,22 +2912,35 @@ not_writing()
 }
 
 /*
- * Check if a buffer is read-only.  Ask for overruling in a dialog.
- * Return TRUE and give an error message when the buffer is readonly.
+ * Check if a buffer is read-only (either 'readonly' option is set or file is
+ * read-only). Ask for overruling in a dialog. Return TRUE and give an error
+ * message when the buffer is readonly.
  */
     static int
 check_readonly(forceit, buf)
     int		*forceit;
     buf_T	*buf;
 {
-    if (!*forceit && buf->b_p_ro)
+    struct stat	st;
+
+    /* Handle a file being readonly when the 'readonly' option is set or when
+     * the file exists and permissions are read-only.
+     * We will send 0777 to check_file_readonly(), as the "perm" variable is
+     * important for device checks but not here. */
+    if (!*forceit && (buf->b_p_ro
+		|| (mch_stat((char *)buf->b_ffname, &st) >= 0
+		    && check_file_readonly(buf->b_ffname, 0777))))
     {
 #if defined(FEAT_GUI_DIALOG) || defined(FEAT_CON_DIALOG)
 	if ((p_confirm || cmdmod.confirm) && buf->b_fname != NULL)
 	{
 	    char_u	buff[IOSIZE];
 
-	    dialog_msg(buff, _("'readonly' option is set for \"%s\".\nDo you wish to write anyway?"),
+	    if (buf->b_p_ro)
+		dialog_msg(buff, _("'readonly' option is set for \"%s\".\nDo you wish to write anyway?"),
+		    buf->b_fname);
+	    else
+		dialog_msg(buff, _("File permissions of \"%s\" are read-only.\nIt may still be possible to write it.\nDo you wish to try?"),
 		    buf->b_fname);
 
 	    if (vim_dialog_yesno(VIM_QUESTION, NULL, buff, 2) == VIM_YES)
@@ -2941,9 +2954,14 @@ check_readonly(forceit, buf)
 	}
 	else
 #endif
+	if (buf->b_p_ro)
 	    EMSG(_(e_readonly));
+	else
+	    EMSG2(_("E505: \"%s\" is read-only (add ! to override)"),
+		    buf->b_fname);
 	return TRUE;
     }
+
     return FALSE;
 }
 

--- a/src/fileio.c
+++ b/src/fileio.c
@@ -424,7 +424,7 @@ readfile(fname, sfname, from, lines_to_s
 	 */
 	if (!p_odev && mch_nodetype(fname) == NODE_WRITABLE)
 	{
-	    filemess(curbuf, fname, (char_u *)_("is a device (disabled with 'opendevice' option"), 0);
+	    filemess(curbuf, fname, (char_u *)_("is a device (disabled with 'opendevice' option)"), 0);
 	    msg_end();
 	    msg_scroll = msg_save;
 	    return FAIL;
@@ -2734,6 +2734,32 @@ set_file_time(fname, atime, mtime)
 #endif
 
 /*
+ * Return TRUE if a file appears to be read-only from the file permissions.
+ */
+    int
+check_file_readonly(fname, perm)
+    char_u	*fname;		/* full path to file */
+    int		perm;		/* known permissions on file */
+{
+#ifndef USE_MCH_ACCESS
+    int	    fd = 0;
+#endif
+
+    return (
+#ifdef USE_MCH_ACCESS
+# ifdef UNIX
+	(perm & 0222) == 0 ||
+# endif
+	mch_access((char *)fname, W_OK)
+#else
+	(fd = mch_open((char *)fname, O_RDWR | O_EXTRA, 0)) < 0
+					? TRUE : (close(fd), FALSE)
+#endif
+	);
+}
+
+
+/*
  * buf_write() - write to file "fname" lines "start" through "end"
  *
  * We do our own buffering here because fwrite() is so slow.
@@ -3219,17 +3245,8 @@ buf_write(buf, fname, sfname, start, end
 	 * Check if the file is really writable (when renaming the file to
 	 * make a backup we won't discover it later).
 	 */
-	file_readonly = (
-# ifdef USE_MCH_ACCESS
-#  ifdef UNIX
-		    (perm & 0222) == 0 ||
-#  endif
-		    mch_access((char *)fname, W_OK)
-# else
-		    (fd = mch_open((char *)fname, O_RDWR | O_EXTRA, 0)) < 0
-						   ? TRUE : (close(fd), FALSE)
-# endif
-		    );
+	file_readonly = check_file_readonly(fname, (int)perm);
+
 	if (!forceit && file_readonly)
 	{
 	    if (vim_strchr(p_cpo, CPO_FWRITE) != NULL)

--- a/src/proto/fileio.pro
+++ b/src/proto/fileio.pro
@@ -2,6 +2,7 @@
 void filemess __ARGS((buf_T *buf, char_u *name, char_u *s, int attr));
 int readfile __ARGS((char_u *fname, char_u *sfname, linenr_T from, linenr_T lines_to_skip, linenr_T lines_to_read, exarg_T *eap, int flags));
 int prep_exarg __ARGS((exarg_T *eap, buf_T *buf));
+int check_file_readonly __ARGS((char_u *fname, int perm));
 int buf_write __ARGS((buf_T *buf, char_u *fname, char_u *sfname, linenr_T start, linenr_T end, exarg_T *eap, int append, int forceit, int reset_changed, int filtering));
 void msg_add_fname __ARGS((buf_T *buf, char_u *fname));
 void msg_add_lines __ARGS((int insert_space, long lnum, long nchars));

--- a/src/version.c
+++ b/src/version.c
@@ -667,6 +667,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    17,
+/**/
     16,
 /**/
     15,