diff --git a/src/screen.c b/src/screen.c
index 18ae8b9..d801c4c 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -6730,7 +6730,7 @@
 	if (wp->w_buffer->b_p_ro)
 	{
 	    STRCPY(p + len, _("[RO]"));
-	    len += 4;
+	    len += (int)STRLEN(p + len);
 	}
 
 	this_ru_col = ru_col - (Columns - W_WIDTH(wp));