diff --git a/test/util-test.cc b/test/util-test.cc
index 6da9553a..2d676a7a 100644
--- a/test/util-test.cc
+++ b/test/util-test.cc
@@ -30,6 +30,7 @@
 #include <cfloat>
 #include <climits>
 #include <cstring>
+#include <functional>
 #include <limits>
 
 #if FMT_USE_TYPE_TRAITS