diff --git a/tests/functional_tests/sha3.cpp b/tests/functional_tests/sha3.cpp
index 537bb5ea..427c1e82 100644
--- a/tests/functional_tests/sha3.cpp
+++ b/tests/functional_tests/sha3.cpp
@@ -23,6 +23,7 @@
 // SOFTWARE.
 #include <iostream>
 #include <iomanip>
+#include <cstdint>
 using namespace std;
 
 #ifndef KECCAKF_ROUNDS