diff --git a/ChangeLog b/ChangeLog
index bdf98804d6..892ba8f5a5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 Thu Oct  7 12:55:04 2004  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
+	* io.c (io_read): should freeze buffer before thread context
+	  switch. [ruby-dev:24442]
+
 	* pack.c (pack_unpack): string conversion should at the top of the
 	  method.  [ruby-dev:24439]
 
diff --git a/io.c b/io.c
index f188f74c11..52e71f3df2 100644
--- a/io.c
+++ b/io.c
@@ -1197,8 +1197,8 @@ io_read(argc, argv, io)
     }
     if (len == 0) return str;
 
-    READ_CHECK(fptr->f);
     FL_SET(str, FL_FREEZE);
+    READ_CHECK(fptr->f);
     n = rb_io_fread(RSTRING(str)->ptr, len, fptr->f);
     FL_UNSET(str, FL_FREEZE);
     if (n == 0) {