diff --git a/src/lread.c b/src/lread.c
index b0eb29a2a1f..5c7bd3993d1 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -2172,7 +2172,10 @@ STREAM or the value of `standard-input' may be:
   if (EQ (stream, Qt))
     stream = Qread_char;
   if (EQ (stream, Qread_char))
-    /* FIXME: ?! When is this used !?  */
+    /* FIXME: ?! This is used when the reader is called from the
+       minibuffer without a stream, as in (read).  But is this feature
+       ever used, and if so, why?  IOW, will anything break if this
+       feature is removed !?  */
     return call1 (intern ("read-minibuffer"),
 		  build_string ("Lisp expression: "));