diff --git a/src/test/permutation.cpp b/src/test/permutation.cpp
index 89e850516..31b83b9d1 100644
--- a/src/test/permutation.cpp
+++ b/src/test/permutation.cpp
@@ -1,4 +1,5 @@
 #include <iostream>
+#include <sstream>
 #include "util/permutation.h"
 #include "util/util.h"