diff --git a/source/datetime.cpp b/source/datetime.cpp
index e6e8fa5b..76e31c1a 100644
--- a/source/datetime.cpp
+++ b/source/datetime.cpp
@@ -15,6 +15,7 @@
 	#include <windows.h>
 #endif
 #include <array>
+#include <ostream>
 
 namespace {
 	std::tm localtime()