diff --git a/src/LarvaDatasets.jl b/src/LarvaDatasets.jl
index 4ddeb45eeb427874dd7ea9f7f1d58db83fa382fc..4f543721ff62173400790e097fd6e43189fa6606 100644
--- a/src/LarvaDatasets.jl
+++ b/src/LarvaDatasets.jl
@@ -271,17 +271,18 @@ function write_larva_dataset_hdf5(path, counts, files, refs, nsteps_before, nste
         end
     end
     h5open(path, "w") do h5
+        g = make_dataset(h5, "samples")
         Threads.foreach(ch) do (file, refs, sampleid)
             @info "Sampling series of spines in run: $(runid(file))"
-            processfile(h5, file, refs, sampleid, nsteps_before, nsteps_after;
+            processfile(g, file, refs, sampleid, nsteps_before, nsteps_after;
                         fixmwt=fixmwt, frameinterval=frameinterval)
         end
-        attributes(h5["samples"])["n_samples"] = sampleid
+        attributes(g)["n_samples"] = sampleid
         # extension
         h5["labels"] = collect(keys(counts))
         #h5["files"] = [f.source for f in files]
         if !isnothing(frameinterval)
-            attributes(h5["samples"])["frame_interval"] = frameinterval
+            attributes(g)["frame_interval"] = frameinterval
         end
     end
 end
@@ -363,7 +364,7 @@ function processfile(h5, file, refs, sampleid, nsteps_before, nsteps_after;
             sample[:,8] = lengths
             sample[:,9:end] = spines
             #
-            name = "samples/sample_$sampleid"
+            name = "sample_$sampleid"
             # transpose for compatibility with h5py
             # see issue https://github.com/JuliaIO/HDF5.jl/issues/785
             h5[name] = permutedims(sample, reverse(1:ndims(sample)))
@@ -517,9 +518,6 @@ function write_larva_dataset_hdf5(output_dir::String,
     h5open(output_file, "cw") do h5
         attributes(h5["samples"])["len_traj"] = window_length
         attributes(h5["samples"])["len_pred"] = window_length
-        if !isnothing(frameinterval)
-            attributes(h5["samples"])["frame_interval"] = frameinterval
-        end
     end
     return output_file
 end