diff --git a/m4/opendev_canonical.m4 b/m4/opendev_canonical.m4
index fe09120..9dccd1e 100644
--- a/m4/opendev_canonical.m4
+++ b/m4/opendev_canonical.m4
@@ -20,7 +20,7 @@ AC_DEFUN([OPENDEV_CANONICAL_TARGET],[
   AX_IS_RELEASE(always)
   AM_SILENT_RULES([yes])
 
-  AX_CXX_COMPILE_STDCXX([17],[],[mandatory])
+  AX_CXX_COMPILE_STDCXX([14],[],[mandatory])
   AM_PROG_CC_C_O
   AC_PROG_CC_STDC
   gl_VISIBILITY
diff --git a/zuul-preview/main.cc b/zuul-preview/main.cc
index d2dc717..42f479d 100644
--- a/zuul-preview/main.cc
+++ b/zuul-preview/main.cc
@@ -19,6 +19,7 @@
 
 #include <config.h>
 #include <pthread.h>
+#include <boost/optional.hpp>
 #include <cpprest/http_client.h>
 #include <bits/stdc++.h>
 
@@ -54,7 +55,7 @@ public:
 
   // Lookup the hostname in the cache and return the URL if present.
   // If the entry is present, it is moved to the head of the queue.
-  optional<const string> get(const string &key)
+  boost::optional<const string> get(const string &key)
   {
     auto location = map.find(key);
     if (location == map.end())