diff --git a/promql/histogram_stats_iterator.go b/promql/histogram_stats_iterator.go
index 87cc5acfbd..f6afb50b61 100644
--- a/promql/histogram_stats_iterator.go
+++ b/promql/histogram_stats_iterator.go
@@ -86,10 +86,14 @@ func (*HistogramStatsIterator) AtHistogram(*histogram.Histogram) (int64, *histog
 // performs a counter reset detection on the fly. It will return an explicit
 // hint (not UnknownCounterReset) if the previous sample has been accessed with
 // the same iterator.
+//
+// The returned histogram contains only Count, Sum, CounterResetHint, and Schema.
+// Bucket data is intentionally omitted.
 func (hsi *HistogramStatsIterator) AtFloatHistogram(fh *histogram.FloatHistogram) (int64, *histogram.FloatHistogram) {
 	populateFH := func(src *histogram.FloatHistogram, detectReset bool) {
 		h := histogram.FloatHistogram{
 			CounterResetHint: src.CounterResetHint,
+			Schema:           src.Schema,
 			Count:            src.Count,
 			Sum:              src.Sum,
 		}
diff --git a/promql/promqltest/testdata/native_histograms.test b/promql/promqltest/testdata/native_histograms.test
index 88ba36c86b..ce473dc69a 100644
--- a/promql/promqltest/testdata/native_histograms.test
+++ b/promql/promqltest/testdata/native_histograms.test
@@ -1118,6 +1118,13 @@ eval instant at 1m30s rate(some_metric[1m30s])
     expect warn msg: PromQL warning: vector contains a mix of histograms with exponential and custom buckets schemas for metric name "some_metric"
     # Should produce no results.
 
+# histogram_count(rate()) must also warn when the schema mix falls inside the stats-only
+# path (HistogramStatsIterator). Without Schema being set in that iterator, all histograms
+# appear as Schema=0 and the custom-bucket mismatch is silently missed.
+eval instant at 1m histogram_count(rate(some_metric[1m30s]))
+    expect warn msg: PromQL warning: vector contains a mix of histograms with exponential and custom buckets schemas for metric name "some_metric"
+    # Should produce no results.
+
 # Start with custom, end with exponential. Return the exponential histogram divided by 48.
 # (The 1st sample is the NHCB with count:1. It is mostly ignored with the exception of the
 # count, which means the rate calculation extrapolates until the count hits 0.)