diff --git a/pageserver/src/page_service.rs b/pageserver/src/page_service.rs
index 6ce716d1d9..74aff21578 100644
--- a/pageserver/src/page_service.rs
+++ b/pageserver/src/page_service.rs
@@ -867,6 +867,10 @@ impl PageServerHandler {
         ctx: &RequestContext,
     ) -> Result<Lsn, PageStreamError> {
         let last_record_lsn = timeline.get_last_record_lsn();
+        // Horizon = 0 (INVALID) is treated as LSN interval degenerated to point [lsn,lsn].
+        // It as done mostly for convenience (because such get_page commands are widely used in tests) and
+        // also seems to be logical: Lsn::MAX moves upper boundary of LSN interval till last_record_lsn and
+        // Lsn(0) moves upper boundary to lower boundary.
         let request_horizon = if horizon == Lsn::INVALID {
             lsn
         } else {
diff --git a/test_runner/regress/test_replication_lag.py b/test_runner/regress/test_replication_lag.py
index 9a5cdafd63..a1521ee7bc 100644
--- a/test_runner/regress/test_replication_lag.py
+++ b/test_runner/regress/test_replication_lag.py
@@ -1,5 +1,4 @@
 import threading
-import time
 
 from fixtures.log_helper import log
 from fixtures.neon_fixtures import NeonEnv, PgBin, wait_replica_caughtup