diff --git a/base/DenseQRUtil.cpp b/base/DenseQRUtil.cpp
index 7e35228c0..9f142b2b3 100644
--- a/base/DenseQRUtil.cpp
+++ b/base/DenseQRUtil.cpp
@@ -17,6 +17,8 @@
  *  Description: the utility functions for DenseQR
  */
 
+#include <cstring>
+
 #include <gtsam/base/timing.h>
 #include <gtsam/base/DenseQRUtil.h>
 #include <boost/numeric/ublas/matrix.hpp>