diff --git a/ChangeLog b/ChangeLog
index 8d3f4a35a3..aad25d44ae 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jul 20 03:42:54 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* thread_pthread.c: use #ifdef, not #if.
+
 Thu Jul 19 15:08:40 2012  Koichi Sasada  <ko1@atdot.net>
 
 	* thread.c (rb_thread_s_control_interrupt,
diff --git a/thread_pthread.c b/thread_pthread.c
index 9075314135..5d24029c56 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -24,7 +24,7 @@
 #elif HAVE_SYS_FCNTL_H
 #include <sys/fcntl.h>
 #endif
-#if HAVE_SYS_PRCTL_H
+#ifdef HAVE_SYS_PRCTL_H
 #include <sys/prctl.h>
 #endif
 #if defined(__native_client__) && defined(NACL_NEWLIB)
@@ -1430,7 +1430,7 @@ ruby_stack_overflowed_p(const rb_thread_t *th, const void *addr)
 int
 rb_reserved_fd_p(int fd)
 {
-#if USE_SLEEPY_TIMER_THRAED
+#ifdef USE_SLEEPY_TIMER_THRAED
     if (fd == timer_thread_pipe[0] ||
 	fd == timer_thread_pipe[1]) {
 	return 1;