diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 289b7288c..d90f03902 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,9 @@
+2011-05-05  Corinna Vinschen  <corinna@vinschen.de>
+
+	* fhandler_disk_file.cc (fhandler_disk_file::pread): Correctly return
+	with errno set to EBADF if file open mode is incorrect.
+	(fhandler_disk_file::pwrite): Ditto.
+
 2011-05-05  Corinna Vinschen  <corinna@vinschen.de>
 
 	* fhandler.cc (is_at_eof): Drop static storage class.  Drop err
diff --git a/winsup/cygwin/fhandler_disk_file.cc b/winsup/cygwin/fhandler_disk_file.cc
index 1c586f3c6..b491fd34f 100644
--- a/winsup/cygwin/fhandler_disk_file.cc
+++ b/winsup/cygwin/fhandler_disk_file.cc
@@ -1415,6 +1415,12 @@ out:
 ssize_t __stdcall
 fhandler_disk_file::pread (void *buf, size_t count, _off64_t offset)
 {
+  if ((get_flags () & O_ACCMODE) == O_WRONLY)
+    {
+      set_errno (EBADF);
+      return -1;
+    }
+
   /* In binary mode, we can use an atomic NtReadFile call. */
   if (rbinary ())
     {
@@ -1476,6 +1482,12 @@ fhandler_disk_file::pread (void *buf, size_t count, _off64_t offset)
 ssize_t __stdcall
 fhandler_disk_file::pwrite (void *buf, size_t count, _off64_t offset)
 {
+  if ((get_flags () & O_ACCMODE) == O_RDONLY)
+    {
+      set_errno (EBADF);
+      return -1;
+    }
+
   /* In binary mode, we can use an atomic NtWriteFile call. */
   if (wbinary ())
     {