diff --git a/Eigen/Core b/Eigen/Core
index 1af04a7ee..3abf6e254 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -119,13 +119,18 @@
 #include <complex>
 #include <cassert>
 #include <functional>
-#include <iostream>
+#include <iosfwd>
 #include <cstring>
 #include <string>
 #include <limits>
 // for min/max:
 #include <algorithm>
 
+// for outputting debug info
+#ifdef EIGEN_DEBUG_ASSIGN
+#include<iostream>
+#endif
+
 #if (defined(_CPPUNWIND) || defined(__EXCEPTIONS)) && !defined(EIGEN_NO_EXCEPTIONS)
   #define EIGEN_EXCEPTIONS
 #endif
diff --git a/Eigen/Eigen2Support b/Eigen/Eigen2Support
index bd6306aff..26b547b9b 100644
--- a/Eigen/Eigen2Support
+++ b/Eigen/Eigen2Support
@@ -26,7 +26,7 @@
 #define EIGEN2SUPPORT_H
 
 #if (!defined(EIGEN2_SUPPORT)) || (!defined(EIGEN_CORE_H))
-#error Eigen2 support must be enabled by defining EIGEN2_SUPPORT before any other Eigen header
+#error Eigen2 support must be enabled by defining EIGEN2_SUPPORT before including any Eigen header
 #endif
 
 #include "src/Core/util/DisableMSVCWarnings.h"
@@ -36,6 +36,7 @@ namespace Eigen {
 /** \defgroup Eigen2Support_Module Eigen2 support module
   * This module provides a couple of deprecated functions improving the compatibility with Eigen2.
   *
+  * To use it, define EIGEN2_SUPPORT before including any Eigen header
   * \code
   * #define EIGEN2_SUPPORT
   * \endcode
@@ -51,4 +52,7 @@ namespace Eigen {
 
 #include "src/Core/util/EnableMSVCWarnings.h"
 
+// Eigen2 used to include iostream
+#include<iostream>
+
 #endif // EIGEN2SUPPORT_H
diff --git a/Eigen/src/Core/Assign.h b/Eigen/src/Core/Assign.h
index f806ba572..eb7bca1da 100644
--- a/Eigen/src/Core/Assign.h
+++ b/Eigen/src/Core/Assign.h
@@ -105,6 +105,7 @@ public:
               : int(NoUnrolling)
   };
 
+#ifdef EIGEN_DEBUG_ASSIGN
   static void debug()
   {
     EIGEN_DEBUG_VAR(DstIsAligned)
@@ -125,6 +126,7 @@ public:
     EIGEN_DEBUG_VAR(MayUnrollInner)
     EIGEN_DEBUG_VAR(Unrolling)
   }
+#endif
 };
 
 /***************************************************************************
diff --git a/test/vectorization_logic.cpp b/test/vectorization_logic.cpp
index ae9911831..94a8a5c96 100644
--- a/test/vectorization_logic.cpp
+++ b/test/vectorization_logic.cpp
@@ -22,6 +22,7 @@
 // License and a copy of the GNU General Public License along with
 // Eigen. If not, see <http://www.gnu.org/licenses/>.
 
+#define EIGEN_DEBUG_ASSIGN
 #include "main.h"
 #include <typeinfo>