diff --git a/unsupported/test/FFTW.cpp b/unsupported/test/FFTW.cpp
index cfe559ebd..a39831a13 100644
--- a/unsupported/test/FFTW.cpp
+++ b/unsupported/test/FFTW.cpp
@@ -8,6 +8,7 @@
 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 #include "main.h"
+#include <cstdint>
 #include <unsupported/Eigen/FFT>
 
 template <typename T>