diff --git a/Misc/NEWS b/Misc/NEWS
index 9b8fc27..2d790f2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -201,6 +201,8 @@
 Build
 -----
 
+- Disable _XOPEN_SOURCE on NetBSD 1.x.
+
 - Bug #1578513: Cross compilation was broken by a change to configure.
   Repair so that it's back to how it was in 2.4.3.
 
diff --git a/configure b/configure
index 8b4e544..3f8459d 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 52455 .
+# From configure.in Revision: 52457 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.59 for python 2.5.
 #
@@ -1555,6 +1555,11 @@
   # Reconfirmed for OpenBSD 3.3 by Zachary Hamm, for 3.4 by Jason Ish.
   OpenBSD/2.* | OpenBSD/3.[0123456789] | OpenBSD/4.[0])
     define_xopen_source=no;;
+  # Defining _XOPEN_SOURCE on NetBSD version prior to the introduction of
+  # _NETBSD_SOURCE disables certain features (eg. setgroups). Reported by
+  # Marc Recht
+  NetBSD/1.5 | NetBSD/1.5.* | NetBSD/1.6 | NetBSD/1.6.* | NetBSD/1.6A-S)
+    define_xopen_source=no;;
   # On Solaris 2.6, sys/wait.h is inconsistent in the usage
   # of union __?sigval. Reported by Stuart Bishop.
   SunOS/5.6)
diff --git a/configure.in b/configure.in
index cd9161b..9d446c6 100644
--- a/configure.in
+++ b/configure.in
@@ -203,6 +203,11 @@
   # Reconfirmed for OpenBSD 3.3 by Zachary Hamm, for 3.4 by Jason Ish.
   OpenBSD/2.* | OpenBSD/3.@<:@0123456789@:>@ | OpenBSD/4.@<:@0@:>@) 
     define_xopen_source=no;;
+  # Defining _XOPEN_SOURCE on NetBSD version prior to the introduction of
+  # _NETBSD_SOURCE disables certain features (eg. setgroups). Reported by
+  # Marc Recht
+  NetBSD/1.5 | NetBSD/1.5.* | NetBSD/1.6 | NetBSD/1.6.* | NetBSD/1.6[A-S])
+    define_xopen_source=no;;
   # On Solaris 2.6, sys/wait.h is inconsistent in the usage
   # of union __?sigval. Reported by Stuart Bishop.
   SunOS/5.6)