diff --git a/ChangeLog b/ChangeLog
index 7f8d338b84..8381daa200 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+Sat May 31 21:15:43 2014  URABE Shyouhei  <shyouhei@ruby-lang.org>
+
+	* thread.c (rb_thread_atfork_internal): My compiler complains
+	  about this variable being used before initialized. I looked at
+	  the code and expanded the macro and turned out it was actually
+	  USED for pointer arithmetic, not dereferenced.  So this was
+	  never a serious bug.  But is annoying indeed to see warnings
+	  every time.  I added `=0` and all went healthy.
+
+	* configure.in: Also, I found that the problematic macro expansion
+	  only happens when we lack __typeof__ C extension, which shall
+	  not be the case of my compiler.  I added AC_CTYPEOF to kick ass.
+
 Sat May 31 16:32:50 2014  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
 
 	* lib/ipaddr.rb: extracted inline tests into test dir.
diff --git a/configure.in b/configure.in
index 97f777972a..11b0f1f58c 100644
--- a/configure.in
+++ b/configure.in
@@ -1188,6 +1188,7 @@ AC_C_CONST
 AC_C_CHAR_UNSIGNED
 AC_C_INLINE
 AC_C_VOLATILE
+AC_C_TYPEOF
 
 AS_CASE(":$ac_cv_c_const:$ac_cv_c_volatile:",
     [*:no:*], [AC_MSG_ERROR(ANSI C-conforming const and volatile are mandatory)])
diff --git a/thread.c b/thread.c
index e4166b5b95..07d65aaf7f 100644
--- a/thread.c
+++ b/thread.c
@@ -3770,7 +3770,7 @@ static void
 rb_thread_atfork_internal(void (*atfork)(rb_thread_t *, const rb_thread_t *))
 {
     rb_thread_t *th = GET_THREAD();
-    rb_thread_t *i;
+    rb_thread_t *i = 0;
     rb_vm_t *vm = th->vm;
     vm->main_thread = th;