diff --git a/prompb/io/prometheus/client/metrics.proto b/prompb/io/prometheus/client/metrics.proto
index 8787f1e229..20858f33db 100644
--- a/prompb/io/prometheus/client/metrics.proto
+++ b/prompb/io/prometheus/client/metrics.proto
@@ -75,6 +75,7 @@ message Histogram {
   repeated Bucket bucket    = 3; // Ordered in increasing order of upper_bound, +Inf bucket is optional.
 
   // Everything below here is for native histograms (also known as sparse histograms).
+  // Native histograms are an experimental feature without stability guarantees.
 
   // schema defines the bucket schema. Currently, valid numbers are -4 <= n <= 8.
   // They are all for base-2 bucket schemas, where 1 is a bucket boundary in each case, and