diff --git a/Misc/NEWS b/Misc/NEWS
index 85af2acf3e7..730e8e0e09b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -1209,6 +1209,9 @@ Library
 Build
 -----
 
+- Issue #12852: Set _XOPEN_SOURCE to 700, instead of 600, to get POSIX 2008
+  functions on OpenBSD (e.g. fdopendir).
+
 - Issue #11863: Remove support for legacy systems deprecated in Python 3.2
   (following PEP 11).  These systems are systems using Mach C Threads,
   SunOS lightweight processes, GNU pth threads and IRIX threads.
diff --git a/configure b/configure
index d1436e06395..51b0114da26 100755
--- a/configure
+++ b/configure
@@ -3140,8 +3140,9 @@ esac
 
 if test $define_xopen_source = yes
 then
+  # X/Open 7, incorporating POSIX.1-2008
 
-$as_echo "#define _XOPEN_SOURCE 600" >>confdefs.h
+$as_echo "#define _XOPEN_SOURCE 700" >>confdefs.h
 
 
   # On Tru64 Unix 4.0F, defining _XOPEN_SOURCE also requires
diff --git a/configure.in b/configure.in
index 5b0f11e53f3..f9be64a9d13 100644
--- a/configure.in
+++ b/configure.in
@@ -397,7 +397,8 @@ esac
 
 if test $define_xopen_source = yes
 then
-  AC_DEFINE(_XOPEN_SOURCE, 600, 
+  # X/Open 7, incorporating POSIX.1-2008
+  AC_DEFINE(_XOPEN_SOURCE, 700,
             Define to the level of X/Open that your system supports)
 
   # On Tru64 Unix 4.0F, defining _XOPEN_SOURCE also requires