diff --git a/ChangeLog b/ChangeLog
index 0c6fcf3ffa..ddd6a22828 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Aug 25 21:02:15 2013  Tanaka Akira  <akr@fsij.org>
+
+	* sizes.c (Init_sizes): Define the size of clock_t.
+
 Sun Aug 25 01:47:47 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (BARY_SHORT_MUL): Renamed from BARY_MUL1.
diff --git a/sizes.c b/sizes.c
index 99ef5a09e6..629978dc00 100644
--- a/sizes.c
+++ b/sizes.c
@@ -41,6 +41,9 @@ Init_sizes(void)
 #if SIZEOF_TIME_T != 0
     DEFINE(time_t, TIME_T);
 #endif
+#if SIZEOF_CLOCK_T != 0
+    DEFINE(clock_t, CLOCK_T);
+#endif
 #if SIZEOF_SIZE_T != 0
     DEFINE(size_t, SIZE_T);
 #endif