diff --git a/Lib/test/test_fcntl.py b/Lib/test/test_fcntl.py
index 58a57b5..2d800b2 100755
--- a/Lib/test/test_fcntl.py
+++ b/Lib/test/test_fcntl.py
@@ -25,7 +25,7 @@
                     'freebsd2', 'freebsd3', 'freebsd4', 'freebsd5',
                     'freebsd6', 'freebsd7',
                     'bsdos2', 'bsdos3', 'bsdos4',
-                    'openbsd', 'openbsd2', 'openbsd3'):
+                    'openbsd', 'openbsd2', 'openbsd3', 'openbsd4'):
     if struct.calcsize('l') == 8:
         off_t = 'l'
         pid_t = 'i'
diff --git a/Lib/test/test_tempfile.py b/Lib/test/test_tempfile.py
index aeaa77e..2047a63 100644
--- a/Lib/test/test_tempfile.py
+++ b/Lib/test/test_tempfile.py
@@ -27,7 +27,7 @@
 # number of files that can be opened at one time (see ulimit -n)
 if sys.platform == 'mac':
     TEST_FILES = 32
-elif sys.platform == 'openbsd3':
+elif sys.platform in ('openbsd3', 'openbsd4'):
     TEST_FILES = 48
 else:
     TEST_FILES = 100
diff --git a/Misc/NEWS b/Misc/NEWS
index 76c4eed..394d921 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -69,6 +69,8 @@
 Build
 -----
 
+- Patch #1540470, for OpenBSD 4.0.
+
 - Patch #1545507: Exclude ctypes package in Win64 MSI file.
 
 - Fix OpenSSL debug build process.
diff --git a/configure b/configure
index 8da9b5e..794a0be 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 47267 .
+# From configure.in Revision: 51173 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.59 for python 2.5.
 #
@@ -1553,7 +1553,7 @@
   # On OpenBSD, select(2) is not available if _XOPEN_SOURCE is defined,
   # even though select is a POSIX function. Reported by J. Ribbens.
   # Reconfirmed for OpenBSD 3.3 by Zachary Hamm, for 3.4 by Jason Ish.
-  OpenBSD/2.* | OpenBSD/3.[0123456789])
+  OpenBSD/2.* | OpenBSD/3.[0123456789] | OpenBSD/4.[0])
     define_xopen_source=no;;
   # On Solaris 2.6, sys/wait.h is inconsistent in the usage
   # of union __?sigval. Reported by Stuart Bishop.
diff --git a/configure.in b/configure.in
index 542463e..410f1af 100644
--- a/configure.in
+++ b/configure.in
@@ -201,7 +201,7 @@
   # On OpenBSD, select(2) is not available if _XOPEN_SOURCE is defined,
   # even though select is a POSIX function. Reported by J. Ribbens.
   # Reconfirmed for OpenBSD 3.3 by Zachary Hamm, for 3.4 by Jason Ish.
-  OpenBSD/2.* | OpenBSD/3.@<:@0123456789@:>@) 
+  OpenBSD/2.* | OpenBSD/3.@<:@0123456789@:>@ | OpenBSD/4.@<:@0@:>@) 
     define_xopen_source=no;;
   # On Solaris 2.6, sys/wait.h is inconsistent in the usage
   # of union __?sigval. Reported by Stuart Bishop.