* even though the _Flags default to the corrected value, still correct

them in the ei_traits, so that they're guaranteed even if the user
  specified his own non-default flags (like before).

  Measured to not make compilation any slower.

Eigen/src/Core/Matrix.h

@@ -87,7 +87,11 @@ struct ei_traits<Matrix<_Scalar, _Rows, _Cols, _MaxRows, _MaxCols, _Flags> >
     ColsAtCompileTime = _Cols,
     MaxRowsAtCompileTime = _MaxRows,
     MaxColsAtCompileTime = _MaxCols,
-    Flags = _Flags,
+    Flags = ei_corrected_matrix_flags<
+                _Scalar,
+                ei_size_at_compile_time<_MaxRows,_MaxCols>::ret,
+                _Flags
+            >::ret,
     CoeffReadCost = NumTraits<Scalar>::ReadCost
   };
 };