1 files changed, 1 insertions, 0 deletions
diff --git a/Eigen/Core b/Eigen/Core
index bb8ad464d..688361d46 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -72,6 +72,7 @@
 #include <cmath>
 #include <cassert>
 #include <functional>
+#include <sstream>
 #ifndef EIGEN_NO_IO
   #include <iosfwd>
 #endif