diff --git a/nt/config.nt b/nt/config.nt
index a4e2c167cf9..ec9a1bd1a0b 100644
--- a/nt/config.nt
+++ b/nt/config.nt
@@ -239,6 +239,8 @@ Boston, MA 02111-1307, USA.  */
 #undef HAVE_GETCWD
 #undef HAVE_SHUTDOWN
 #undef HAVE_STRFTIME
+/* Standard Windows strftime does not support POSIX.2 extensions.  */
+#define STRFTIME_NO_POSIX2 1
 
 #define LOCALTIME_CACHE
 #undef HAVE_INET_SOCKETS
diff --git a/src/config.in b/src/config.in
index b08515b3d70..6a504ea3251 100644
--- a/src/config.in
+++ b/src/config.in
@@ -293,6 +293,7 @@ Boston, MA 02111-1307, USA.  */
 #undef HAVE_GETWD
 #undef HAVE_SHUTDOWN
 #undef HAVE_STRFTIME
+#undef STRFTIME_NO_POSIX2
 #undef HAVE_GETADDRINFO
 #undef HAVE___FPENDING
 #undef HAVE_FSEEKO