diff --git a/src/determinants/spindeterminants.irp.f b/src/determinants/spindeterminants.irp.f
index 01979c02..2f497bd7 100644
--- a/src/determinants/spindeterminants.irp.f
+++ b/src/determinants/spindeterminants.irp.f
@@ -197,7 +197,9 @@ integer function get_index_in_psi_det_alpha_unique(key,Nint)
   enddo
   i += 1
 
-  ASSERT (i <= N_det_alpha_unique)
+  if (i> N_det_alpha_unique) then
+    call qp_bug(irp_here, i, 'i> N_det_alpha_unique')
+  endif
 
   !DIR$ FORCEINLINE
   do while (spin_det_search_key(psi_det_alpha_unique(1,i),Nint) == det_ref)
@@ -219,12 +221,15 @@ integer function get_index_in_psi_det_alpha_unique(key,Nint)
     endif
     i += 1
     if (i > N_det_alpha_unique) then
-      ASSERT (get_index_in_psi_det_alpha_unique > 0)
-      return
+      exit
     endif
 
   enddo
 
+  if (get_index_in_psi_det_alpha_unique <= 0) then
+    call qp_bug(irp_here, get_index_in_psi_det_alpha_unique, 'get_index_in_psi_det_alpha_unique <= 0')
+  endif
+
 end
 
 integer function get_index_in_psi_det_beta_unique(key,Nint)
@@ -277,7 +282,9 @@ integer function get_index_in_psi_det_beta_unique(key,Nint)
   enddo
   i += 1
 
-  ASSERT (i <= N_det_beta_unique)
+  if (i > N_det_beta_unique) then
+    call qp_bug(irp_here, i, 'i> N_det_beta_unique')
+  endif
 
   !DIR$ FORCEINLINE
   do while (spin_det_search_key(psi_det_beta_unique(1,i),Nint) == det_ref)
@@ -299,12 +306,15 @@ integer function get_index_in_psi_det_beta_unique(key,Nint)
     endif
     i += 1
     if (i > N_det_beta_unique) then
-      ASSERT (get_index_in_psi_det_beta_unique > 0)
-      return
+      exit
     endif
 
   enddo
 
+  if (get_index_in_psi_det_beta_unique <= 0) then
+    call qp_bug(irp_here, i, 'get_index_in_psi_det_beta_unique <= 0')
+  endif
+
 end
 
 
diff --git a/src/utils/bug.irp.f b/src/utils/bug.irp.f
new file mode 100644
index 00000000..0e2ad551
--- /dev/null
+++ b/src/utils/bug.irp.f
@@ -0,0 +1,23 @@
+subroutine qp_bug(from, code, message)
+  implicit none
+  BEGIN_DOC
+! This routine prints a bug report
+  END_DOC
+  character*(*) :: from
+  integer :: code
+  character*(*) :: message
+
+  print *, ''
+  print *, '======================='
+  print *, 'Bug in Quantum Package!'
+  print *, '======================='
+  print *, ''
+  print *, '   from: ', trim(from)
+  print *, '   code: ', code
+  print *, '   info: ', trim(message)
+  print *, ''
+  print *, 'Please report this bug at https://github.com/QuantumPackage/qp2/issues'
+  print *, 'with your output file attached.'
+  print *, ''
+  stop -1
+end subroutine qp_bug