diff --git a/src/scf_utils/diagonalize_fock.irp.f b/src/scf_utils/diagonalize_fock.irp.f
index 865b4d31..288fb3e8 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)
 
@@ -83,7 +85,7 @@ BEGIN_PROVIDER [ double precision, eigenvectors_Fock_matrix_mo, (ao_num,mo_num)
    call dgemm('N','N',ao_num,mo_num,mo_num, 1.d0,            &
        mo_coef, size(mo_coef,1), F, size(F,1),                       &
        0.d0, eigenvectors_Fock_matrix_mo, size(eigenvectors_Fock_matrix_mo,1))
-   deallocate(work, F, diag)
+   deallocate(work, F, F_save, diag)
 
 
 END_PROVIDER