diff --git a/configure b/configure
index bc59e81e2887..205a75bb33bc 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 43536 .
+# From configure.in Revision: 43604 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.59 for python 2.5.
 #
@@ -1511,14 +1511,18 @@ case $ac_sys_system/$ac_sys_release in
       define_xopen_source=no
     fi
     ;;
-  # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
-  # disables platform specific features beyond repair.
+  # XXX(nnorwitz): the 2 cases below should be Darwin/[78].*,
+  # but autoconf seems to convert that to Darwin/78.* which is incorrect.
   # On Mac OS X 10.3, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
-  # has no effect, don't bother defineing them
-  Darwin/78.*)
+  # has no effect, don't bother defining them.
+  Darwin/7.*)
+    define_xopen_source=no
+    ;;
+  # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
+  # disables platform specific features beyond repair.
+  Darwin/8.*)
     define_xopen_source=no
     ;;
-
 esac
 
 if test $define_xopen_source = yes
diff --git a/configure.in b/configure.in
index 12ac14919a88..4fb6cea765e2 100644
--- a/configure.in
+++ b/configure.in
@@ -171,14 +171,18 @@ case $ac_sys_system/$ac_sys_release in
       define_xopen_source=no
     fi
     ;;
-  # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
-  # disables platform specific features beyond repair.
+  # XXX(nnorwitz): the 2 cases below should be Darwin/[78].*, 
+  # but autoconf seems to convert that to Darwin/78.* which is incorrect.
   # On Mac OS X 10.3, defining _POSIX_C_SOURCE or _XOPEN_SOURCE 
-  # has no effect, don't bother defineing them
-  Darwin/[78].*)
+  # has no effect, don't bother defining them.
+  Darwin/7.*)
+    define_xopen_source=no
+    ;;
+  # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
+  # disables platform specific features beyond repair.
+  Darwin/8.*)
     define_xopen_source=no
     ;;
-
 esac
 
 if test $define_xopen_source = yes