diff --git a/ChangeLog b/ChangeLog
index bb1dea3cc3..afacc5cdf8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sat Jan  7 06:24:18 2006  Tanaka Akira  <akr@m17n.org>
+
+	* eval.c (rb_fd_isset): compare the result of FD_ISSET with 0 to
+	  avoid BSD bug.  BSD defines FD_ISSET as just a bitmap of unsigned
+	  long.  So returning the value from rb_fd_isset discards upper
+	  32bits on LP64 environment.
+	  http://www.freebsd.org/cgi/query-pr.cgi?pr=ia64/91421
+
 Fri Jan  6 02:20:18 2006  Tanaka Akira  <akr@m17n.org>
 
 	* configure.in: don't force getcontext on IA64.
diff --git a/eval.c b/eval.c
index 61f38e56f9..4705e06d25 100644
--- a/eval.c
+++ b/eval.c
@@ -9644,7 +9644,7 @@ rb_fd_isset(n, fds)
     const rb_fdset_t *fds;
 {
     if (n >= fds->maxfd) return 0;
-    return FD_ISSET(n, fds->fdset);
+    return FD_ISSET(n, fds->fdset) != 0; /* "!= 0" avoids BSD bug */
 }
 
 void