diff --git a/tests/unit-tests/util/sha256.t.cpp b/tests/unit-tests/util/sha256.t.cpp
index 6e42201..2fec00f 100644
--- a/tests/unit-tests/util/sha256.t.cpp
+++ b/tests/unit-tests/util/sha256.t.cpp
@@ -25,6 +25,8 @@
 
 #include "boost-test.hpp"
 
+#include <sstream>
+
 namespace ndn {
 namespace util {
 namespace test {