diff --git a/src/vt/vrt/collection/types/untyped.h b/src/vt/vrt/collection/types/untyped.h
index 87d4e68fcb..c17ae00b46 100644
--- a/src/vt/vrt/collection/types/untyped.h
+++ b/src/vt/vrt/collection/types/untyped.h
@@ -48,6 +48,8 @@
 #include "vt/vrt/base/base.h"
 #include "vt/vrt/collection/types/has_migrate.h"
 
+#include <unordered_set>
+
 namespace vt { namespace vrt { namespace collection {
 
 /*