includes: sort all includes
diff --git a/src/unittest/cprintftime.cc b/src/unittest/cprintftime.cc
index f35e0aa..3192d8e 100644
--- a/src/unittest/cprintftime.cc
+++ b/src/unittest/cprintftime.cc
@@ -30,8 +30,8 @@
 
 #include <iostream>
 #include <list>
-#include <string>
 #include <sstream>
+#include <string>
 
 #include "base/cprintf.hh"