diff -up ./libs/base/include/mrpt/math/eigen_plugins.h.eigen306 ./libs/base/include/mrpt/math/eigen_plugins.h
--- ./libs/base/include/mrpt/math/eigen_plugins.h.eigen306	2013-01-04 18:23:15.000000000 -0500
+++ ./libs/base/include/mrpt/math/eigen_plugins.h	2013-04-13 13:14:34.512745092 -0400
@@ -33,6 +33,9 @@
    | POSSIBILITY OF SUCH DAMAGE.                                               |
    +---------------------------------------------------------------------------+ */
 
+#ifndef EIGEN_PLUGIN_H
+#define EIGEN_PLUGIN_H
+
 // -------------------------------------------------------------------------
 // Note: This file will be included within the body of Eigen::MatrixBase
 // -------------------------------------------------------------------------
@@ -868,4 +871,4 @@ public:
 			for (size_t dst_col_blk=0;dst_col_blk<N; ++dst_col_blk )
 				out.coeffRef(dst_row_blk,dst_col_blk) = this->coeff(indices[dst_row_blk],indices[dst_col_blk]);
 	}
-
+#endif