diff --git a/src/fof_catalogue_io.c b/src/fof_catalogue_io.c
index e7410a0b1707ad83e0a86bccc4a684c813432687..e437492209b65d405fa0331b5c08c9d4cde9b76b 100644
--- a/src/fof_catalogue_io.c
+++ b/src/fof_catalogue_io.c
@@ -103,6 +103,8 @@ void write_fof_hdf5_header(hid_t h_file, const struct engine* e,
                      swift_type_count);
   io_write_attribute(h_grp, "NumPart_Total_HighWord", UINT,
                      numParticlesHighWord, swift_type_count);
+  io_write_attribute(h_grp, "TotalNumberOfParticles", LONGLONG, N_total,
+                     swift_type_count);
   double MassTable[swift_type_count] = {0};
   io_write_attribute(h_grp, "MassTable", DOUBLE, MassTable, swift_type_count);
   io_write_attribute(h_grp, "InitialMassTable", DOUBLE,
@@ -113,7 +115,13 @@ void write_fof_hdf5_header(hid_t h_file, const struct engine* e,
                      swift_type_count);
   io_write_attribute_i(h_grp, "NumFilesPerSnapshot", e->nr_nodes);
   io_write_attribute_i(h_grp, "ThisFile", e->nodeID);
+  io_write_attribute_s(h_grp, "SelectOutput", "Default");
+  io_write_attribute_i(h_grp, "Virtual", 0);
+  const int to_write[swift_type_count] = {0};
+  io_write_attribute(h_grp, "CanHaveTypes", INT, to_write, swift_type_count);
   io_write_attribute_s(h_grp, "OutputType", "FOF");
+
+  /* FOF-specific counters */
   io_write_attribute_ll(h_grp, "NumGroups_Total", num_groups_total);
   io_write_attribute_ll(h_grp, "NumGroups_ThisFile", num_groups_this_file);
 
diff --git a/src/line_of_sight.c b/src/line_of_sight.c
index 40ddf3632348b42c8afcae118b2ade1a11947e54..94291770bc7c7be58ddf93b06772418aa5135381 100644
--- a/src/line_of_sight.c
+++ b/src/line_of_sight.c
@@ -524,6 +524,8 @@ void write_hdf5_header(hid_t h_file, const struct engine *e,
                      swift_type_count);
   io_write_attribute(h_grp, "NumPart_Total_HighWord", UINT,
                      numParticlesHighWord, swift_type_count);
+  io_write_attribute(h_grp, "TotalNumberOfParticles", LONGLONG, N_total,
+                     swift_type_count);
   double MassTable[swift_type_count] = {0};
   io_write_attribute(h_grp, "MassTable", DOUBLE, MassTable, swift_type_count);
   io_write_attribute(h_grp, "InitialMassTable", DOUBLE,
@@ -536,6 +538,8 @@ void write_hdf5_header(hid_t h_file, const struct engine *e,
   io_write_attribute_i(h_grp, "ThisFile", 0);
   io_write_attribute_s(h_grp, "SelectOutput", "Default");
   io_write_attribute_i(h_grp, "Virtual", 0);
+  const int to_write[swift_type_count] = {1}; /* We can only have gas */
+  io_write_attribute(h_grp, "CanHaveTypes", INT, to_write, swift_type_count);
   io_write_attribute_s(h_grp, "OutputType", "LineOfSight");
 
   /* Close group */