diff --git a/ChangeLog b/ChangeLog
index 566a209bda..2227df2a95 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Jun 20 02:44:45 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* win32/win32.c (waitpid): should not return 0 but wait until exit
+	  unless WNOHANG is given.  waiting huge process may return while
+	  active, for some reason.
+
 Thu Jun 20 01:34:15 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (bdigit_roomof): Use SIZEOF_BDIGITS.
diff --git a/win32/win32.c b/win32/win32.c
index 7b42df096f..0fc4186fff 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -4153,8 +4153,10 @@ waitpid(rb_pid_t pid, int *stat_loc, int options)
 	    /* wait... */
 	    if (rb_w32_wait_events_blocking(&child->hProcess, 1, timeout) != WAIT_OBJECT_0) {
 		/* still active */
-		pid = 0;
-		break;
+		if (options & WNOHANG) {
+		    pid = 0;
+		    break;
+		}
 	    }
 	}
     }