diff --git a/specification/metrics/sdk.md b/specification/metrics/sdk.md
index 371987b7b38..5d71a8637c5 100644
--- a/specification/metrics/sdk.md
+++ b/specification/metrics/sdk.md
@@ -1033,7 +1033,8 @@ cycle. For the above example, that would mean that the `num_measurements_seen`
 count is reset every time the reservoir is collected.
 
 This Exemplar reservoir MAY take a configuration parameter for the size of the
-reservoir pool.
+reservoir pool. If no size configuration is provided, the default size of `1`
+SHOULD be used.
 
 #### AlignedHistogramBucketExemplarReservoir