diff --git a/ChangeLog b/ChangeLog
index 47d727d3ac3bb3..d0d8bd312968ca 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Mar 27 23:44:11 2012  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* io.c (io_unread): fixed memory leak.  report by nagachika via IRC.
+
 Tue Mar 27 22:44:23 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (verconf.h): separate load path specific stuff from
diff --git a/io.c b/io.c
index d569e4d8d71006..fac42c710b1091 100644
--- a/io.c
+++ b/io.c
@@ -473,6 +473,7 @@ io_unread(rb_io_t *fptr)
 	}
 	read_size = _read(fptr->fd, buf, fptr->rbuf.len + newlines);
 	if (read_size < 0) {
+	    free(buf);
 	    rb_sys_fail_path(fptr->pathv);
 	}
 	if (read_size == fptr->rbuf.len) {
@@ -483,6 +484,7 @@ io_unread(rb_io_t *fptr)
 	    newlines--;
 	}
     }
+    free(buf);
     fptr->rbuf.off = 0;
     fptr->rbuf.len = 0;
     return;