Index: ext/readline/readline.c
===================================================================
--- ext/readline/readline.c	(revision 45224)
+++ ext/readline/readline.c	(revision 45225)
@@ -1974,7 +1974,7 @@
 
     rl_attempted_completion_function = readline_attempted_completion_function;
 #if defined(HAVE_RL_PRE_INPUT_HOOK)
-    rl_pre_input_hook = (Function *)readline_pre_input_hook;
+    rl_pre_input_hook = (rl_hook_func_t *)readline_pre_input_hook;
 #endif
 #ifdef HAVE_RL_CATCH_SIGNALS
     rl_catch_signals = 0;
Index: ext/readline/extconf.rb
===================================================================
--- ext/readline/extconf.rb	(revision 45239)
+++ ext/readline/extconf.rb	(revision 45240)
@@ -19,6 +19,10 @@
   return super(func, headers)
 end
 
+def readline.have_type(type)
+  return super(type, headers)
+end
+
 dir_config('curses')
 dir_config('ncurses')
 dir_config('termcap')
@@ -94,4 +98,8 @@
 readline.have_func("rl_redisplay")
 readline.have_func("rl_insert_text")
 readline.have_func("rl_delete_text")
+unless readline.have_type("rl_hook_func_t")
+  $DEFS << "-Drl_hook_func_t=Function"
+end
+
 create_makefile("readline")
Index: ext/readline/extconf.rb
===================================================================
--- ext/readline/extconf.rb	(revision 45242)
+++ ext/readline/extconf.rb	(revision 45243)
@@ -99,6 +99,9 @@
 readline.have_func("rl_insert_text")
 readline.have_func("rl_delete_text")
 unless readline.have_type("rl_hook_func_t")
+  # rl_hook_func_t is available since readline-4.2 (2001).
+  # Function is removed at readline-6.3 (2014).
+  # However, editline (NetBSD 6.1.3, 2014) doesn't have rl_hook_func_t.
   $DEFS << "-Drl_hook_func_t=Function"
 end