diff --git a/contrib/test_decoding/expected/slot.out b/contrib/test_decoding/expected/slot.out
index 21e9d56f73..3a1a7e8514 100644
--- a/contrib/test_decoding/expected/slot.out
+++ b/contrib/test_decoding/expected/slot.out
@@ -131,3 +131,20 @@ SELECT pg_drop_replication_slot('regression_slot1');
 ERROR:  replication slot "regression_slot1" does not exist
 SELECT pg_drop_replication_slot('regression_slot2');
 ERROR:  replication slot "regression_slot2" does not exist
+-- slot advance with physical slot, error with non-reserved slot
+SELECT slot_name FROM pg_create_physical_replication_slot('regression_slot3');
+    slot_name     
+------------------
+ regression_slot3
+(1 row)
+
+SELECT pg_replication_slot_advance('regression_slot3', '0/0'); -- invalid LSN
+ERROR:  invalid target WAL location (LSN)
+SELECT pg_replication_slot_advance('regression_slot3', '0/1'); -- error
+ERROR:  cannot move slot not reserving WAL
+SELECT pg_drop_replication_slot('regression_slot3');
+ pg_drop_replication_slot 
+--------------------------
+ 
+(1 row)
+
diff --git a/contrib/test_decoding/sql/slot.sql b/contrib/test_decoding/sql/slot.sql
index 706340c1d8..24cdf7155d 100644
--- a/contrib/test_decoding/sql/slot.sql
+++ b/contrib/test_decoding/sql/slot.sql
@@ -68,3 +68,9 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_
 -- both should error as they should be dropped on error
 SELECT pg_drop_replication_slot('regression_slot1');
 SELECT pg_drop_replication_slot('regression_slot2');
+
+-- slot advance with physical slot, error with non-reserved slot
+SELECT slot_name FROM pg_create_physical_replication_slot('regression_slot3');
+SELECT pg_replication_slot_advance('regression_slot3', '0/0'); -- invalid LSN
+SELECT pg_replication_slot_advance('regression_slot3', '0/1'); -- error
+SELECT pg_drop_replication_slot('regression_slot3');
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 3ed9021c2f..4851bc2e24 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -9867,7 +9867,8 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
       <entry></entry>
       <entry>The address (<literal>LSN</literal>) of oldest WAL which still
       might be required by the consumer of this slot and thus won't be
-      automatically removed during checkpoints.
+      automatically removed during checkpoints.  <literal>NULL</literal>
+      if the <literal>LSN</literal> of this slot has never been reserved.
       </entry>
      </row>
 
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 2806e1076c..b55dadfe2f 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -465,7 +465,7 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS)
 
 	if (XLogRecPtrIsInvalid(moveto))
 		ereport(ERROR,
-				(errmsg("invalid target wal lsn")));
+				(errmsg("invalid target WAL location (LSN)")));
 
 	/* Build a tuple descriptor for our result type */
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
@@ -483,6 +483,15 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS)
 	/* Acquire the slot so we "own" it */
 	ReplicationSlotAcquire(NameStr(*slotname), true);
 
+	/* A slot whose restart_lsn has never been reserved cannot be advanced */
+	if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
+	{
+		ReplicationSlotRelease();
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot move slot not reserving WAL")));
+	}
+
 	/*
 	 * Check if the slot is not moving backwards.  Physical slots rely simply
 	 * on restart_lsn as a minimum point, while logical slots have confirmed