diff --git a/Eigen/src/QR/Tridiagonalization.h b/Eigen/src/QR/Tridiagonalization.h
index f56b09128..599786302 100644
--- a/Eigen/src/QR/Tridiagonalization.h
+++ b/Eigen/src/QR/Tridiagonalization.h
@@ -164,7 +164,7 @@ Tridiagonalization<MatrixType>::matrixT(void) const
   // and fill it ? (to avoid temporaries)
   int n = m_matrix.rows();
   MatrixType matT = m_matrix;
-  matT.corner(TopRight,n-1, n-1).diagonal() = subDiagonal().conjugate();
+  matT.corner(TopRight,n-1, n-1).diagonal() = subDiagonal().template cast<Scalar>().conjugate();
   if (n>2)
   {
     matT.corner(TopRight,n-2, n-2).template part<UpperTriangular>().setZero();