diff --git a/Eigen/Core b/Eigen/Core
index efdae86cf..ac7c5b300 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -279,7 +279,10 @@
 #include <cmath>
 #include <cassert>
 #include <functional>
-#include <iosfwd>
+#include <sstream>
+#ifndef EIGEN_NO_IO
+  #include <iosfwd>
+#endif
 #include <cstring>
 #include <string>
 #include <limits>
diff --git a/Eigen/src/Core/arch/CUDA/Half.h b/Eigen/src/Core/arch/CUDA/Half.h
index 755e6209d..59717b4fe 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 {