diff --git a/image_analysis/MXAnalysisWithoutFPGA.cpp b/image_analysis/MXAnalysisWithoutFPGA.cpp
index 5411e0942..67a29a0ea 100644
--- a/image_analysis/MXAnalysisWithoutFPGA.cpp
+++ b/image_analysis/MXAnalysisWithoutFPGA.cpp
@@ -253,10 +253,11 @@ void MXAnalysisWithoutFPGA::Analyze(DataMessage &output,
             // n_indexed^2 / n_total (indexed count weighted by indexed fraction) together with its spot
             // list, and integrate that one. The lattice is searched for once per frame: the first list
             // it is found on hands it to the others, which only refine and score it (FrameIndexerCalls).
-            // The min-pix 1 list is not searched where the min-pix 2 list holds fewer spots than a
-            // lattice needs: such a frame has (almost) no spot of two pixels, and the lattices a search
-            // fits to its single pixels were measured to be spurious - de novo, cells unrelated to the
-            // crystal's; against a known cell, frames that add nothing to the merge.
+            // De novo, the min-pix 1 list is not searched where the min-pix 2 list holds fewer spots than
+            // a lattice needs: such a frame has (almost) no spot of two pixels, and the cells a free search
+            // fits to its single pixels were measured to be unrelated to the crystal's. Against a known
+            // cell it is searched: on sparse serial data those frames are real hits (measured - leaving
+            // them out halved the observations of a weakly diffracting run).
             const auto detect_start_time = std::chrono::steady_clock::now();
             finder.Detect(*preprocessor_buffer, spot_finding_settings);
             const auto &components = finder.ExtractComponents(*preprocessor_buffer, spot_finding_settings);
@@ -282,7 +283,7 @@ void MXAnalysisWithoutFPGA::Analyze(DataMessage &output,
                     mp2_spot_count = std::count_if(output.spots.begin(), output.spots.end(), [&](const auto &spot) {
                         return experiment.GetIndexingSettings().GetIndexIceRings() || !spot.ice_ring;
                     });
-                if (mp == 1 && !frame_calls.lattice_found
+                if (mp == 1 && !frame_calls.lattice_found && !experiment.GetUnitCell().has_value()
                     && mp2_spot_count < experiment.GetIndexingSettings().GetViableCellMinSpots())
                     continue;
                 const bool indexed = indexer.IndexFrameOnly(output, s, &frame_calls);