diff --git a/src/scf_utils/diagonalize_fock.irp.f b/src/scf_utils/diagonalize_fock.irp.f
index 865b4d31..1e6fa1af 100644
--- a/src/scf_utils/diagonalize_fock.irp.f
+++ b/src/scf_utils/diagonalize_fock.irp.f
@@ -7,11 +7,11 @@ BEGIN_PROVIDER [ double precision, eigenvectors_Fock_matrix_mo, (ao_num,mo_num)
    integer                        :: i,j
    integer                        :: liwork, lwork, n, info
    integer, allocatable           :: iwork(:)
-   double precision, allocatable  :: work(:), F(:,:), S(:,:)
+   double precision, allocatable  :: work(:), F(:,:), F_save(:,:)
    double precision, allocatable  :: diag(:)
 
 
-   allocate( F(mo_num,mo_num) )
+   allocate( F(mo_num,mo_num), F_save(mo_num,mo_num)  )
    allocate (diag(mo_num) )
 
    do j=1,mo_num
@@ -51,6 +51,7 @@ BEGIN_PROVIDER [ double precision, eigenvectors_Fock_matrix_mo, (ao_num,mo_num)
    lwork = -1
    liwork = -1
 
+   F_save = F
    call dsyevd( 'V', 'U', mo_num, F,                             &
        size(F,1), diag, work, lwork, iwork, liwork, info)
 
@@ -71,6 +72,7 @@ BEGIN_PROVIDER [ double precision, eigenvectors_Fock_matrix_mo, (ao_num,mo_num)
 
 
    if (info /= 0) then
+     F = F_save
      call dsyev( 'V', 'L', mo_num, F,                            &
          size(F,1), diag, work, lwork, info)
 
diff --git a/src/scf_utils/roothaan_hall_scf.irp.f b/src/scf_utils/roothaan_hall_scf.irp.f
index faf23a51..ea472cdf 100644
--- a/src/scf_utils/roothaan_hall_scf.irp.f
+++ b/src/scf_utils/roothaan_hall_scf.irp.f
@@ -299,6 +299,7 @@ END_DOC
           Fock_matrix_AO_(i,j) = 0.d0
         enddo
         do k=1,dim_DIIS
+          if (dabs(X_vector_DIIS(k)) < 1.d-10) cycle
           do i=1,ao_num
             Fock_matrix_AO_(i,j) = Fock_matrix_AO_(i,j) +            &
                 X_vector_DIIS(k)*Fock_matrix_DIIS(i,j,dim_DIIS-k+1)