diff --git a/Eigen/Core b/Eigen/Core
index 0f7fa63..ac7e394 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -260,6 +260,7 @@
 #include <cmath>
 #include <cassert>
 #include <functional>
+#include <sstream>
 #include <iosfwd>
 #include <cstring>
 #include <string>
diff --git a/Eigen/src/Core/arch/CUDA/Half.h b/Eigen/src/Core/arch/CUDA/Half.h
index 294c517..88dd385 100644
--- a/Eigen/src/Core/arch/CUDA/Half.h
+++ b/Eigen/src/Core/arch/CUDA/Half.h
@@ -42,6 +42,7 @@
 #define EIGEN_EXPLICIT_CAST(tgt_type) operator tgt_type()
 #endif
 
+#include <sstream>
 
 namespace Eigen {