diff --git a/ChangeLog b/ChangeLog
index f2fbc0b0b7..a8d18620bf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jul 11 23:22:28 2011  Yutaka Kanemoto  <kanemoto@ruby-lang.org>
+
+	* time.c: can't compile time.c on AIX due to missing declaration for
+	  ffs(). It is declared in strings.h on AIX.
+
 Mon Jul 11 15:54:24 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* process.c: removed signal() macro. It's no longer used.
diff --git a/time.c b/time.c
index 5dbf9b22ca..95bdb1f504 100644
--- a/time.c
+++ b/time.c
@@ -23,6 +23,10 @@
 #include <float.h>
 #include <math.h>
 
+#ifdef HAVE_STRINGS_H
+#include <strings.h>
+#endif
+
 #include "timev.h"
 
 static ID id_divmod, id_mul, id_submicro, id_nano_num, id_nano_den, id_offset;