diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 38c82c4619..92430439f5 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -374,7 +374,16 @@ perform_base_backup(basebackup_options *opt, bbsink *sink)
 				Assert(lnext(state.tablespaces, lc) == NULL);
 			}
 			else
+			{
+				/* Properly terminate the tarfile. */
+				StaticAssertStmt(TAR_BLOCK_SIZE <= 2 * BLCKSZ,
+								 "BLCKSZ too small for 2 tar blocks");
+				memset(sink->bbs_buffer, 0, 2 * TAR_BLOCK_SIZE);
+				bbsink_archive_contents(sink, 2 * TAR_BLOCK_SIZE);
+
+				/* OK, that's the end of the archive. */
 				bbsink_end_archive(sink);
+			}
 		}
 
 		basebackup_progress_wait_wal_archive(&state);
@@ -611,6 +620,13 @@ perform_base_backup(basebackup_options *opt, bbsink *sink)
 			sendFileWithContent(sink, pathbuf, "", &manifest);
 		}
 
+		/* Properly terminate the tar file. */
+		StaticAssertStmt(TAR_BLOCK_SIZE <= 2 * BLCKSZ,
+						 "BLCKSZ too small for 2 tar blocks");
+		memset(sink->bbs_buffer, 0, 2 * TAR_BLOCK_SIZE);
+		bbsink_archive_contents(sink, 2 * TAR_BLOCK_SIZE);
+
+		/* OK, that's the end of the archive. */
 		bbsink_end_archive(sink);
 	}
 
diff --git a/src/bin/pg_basebackup/bbstreamer_tar.c b/src/bin/pg_basebackup/bbstreamer_tar.c
index 5fded0f4e6..e6bd3ef52e 100644
--- a/src/bin/pg_basebackup/bbstreamer_tar.c
+++ b/src/bin/pg_basebackup/bbstreamer_tar.c
@@ -2,6 +2,16 @@
  *
  * bbstreamer_tar.c
  *
+ * This module implements three types of tar processing. A tar parser
+ * expects unlabelled chunks of data (e.g. BBSTREAMER_UNKNOWN) and splits
+ * it into labelled chunks (any other value of bbstreamer_archive_context).
+ * A tar archiver does the reverse: it takes a bunch of labelled chunks
+ * and produces a tarfile, optionally replacing member headers and trailers
+ * so that upstream bbstreamer objects can perform surgery on the tarfile
+ * contents without knowing the details of the tar format. A tar terminator
+ * just adds two blocks of NUL bytes to the end of the file, since older
+ * server versions produce files with this terminator omitted.
+ *
  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 30efc03b83..1739ac6382 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -85,6 +85,12 @@ typedef void (*WriteDataCallback) (size_t nbytes, char *buf,
  */
 #define MINIMUM_VERSION_FOR_MANIFESTS	130000
 
+/*
+ * Before v15, tar files received from the server will be improperly
+ * terminated.
+ */
+#define MINIMUM_VERSION_FOR_TERMINATED_TARFILE 150000
+
 /*
  * Different ways to include WAL
  */
@@ -166,7 +172,8 @@ static void progress_report(int tablespacenum, bool force, bool finished);
 
 static bbstreamer *CreateBackupStreamer(char *archive_name, char *spclocation,
 										bbstreamer **manifest_inject_streamer_p,
-										bool is_recovery_guc_supported);
+										bool is_recovery_guc_supported,
+										bool expect_unterminated_tarfile);
 static void ReceiveTarFile(PGconn *conn, char *archive_name, char *spclocation,
 						   bool tablespacenum);
 static void ReceiveTarCopyChunk(size_t r, char *copybuf, void *callback_data);
@@ -965,7 +972,8 @@ ReceiveCopyData(PGconn *conn, WriteDataCallback callback,
 static bbstreamer *
 CreateBackupStreamer(char *archive_name, char *spclocation,
 					 bbstreamer **manifest_inject_streamer_p,
-					 bool is_recovery_guc_supported)
+					 bool is_recovery_guc_supported,
+					 bool expect_unterminated_tarfile)
 {
 	bbstreamer *streamer;
 	bbstreamer *manifest_inject_streamer = NULL;
@@ -1074,12 +1082,13 @@ CreateBackupStreamer(char *archive_name, char *spclocation,
 	/*
 	 * If we're doing anything that involves understanding the contents of
 	 * the archive, we'll need to parse it. If not, we can skip parsing it,
-	 * but the tar files the server sends are not properly terminated, so
-	 * we'll need to add the terminator here.
+	 * but old versions of the server send improperly terminated tarfiles,
+	 * so if we're talking to such a server we'll need to add the terminator
+	 * here.
 	 */
 	if (must_parse_archive)
 		streamer = bbstreamer_tar_parser_new(streamer);
-	else
+	else if (expect_unterminated_tarfile)
 		streamer = bbstreamer_tar_terminator_new(streamer);
 
 	/* Return the results. */
@@ -1099,14 +1108,18 @@ ReceiveTarFile(PGconn *conn, char *archive_name, char *spclocation,
 	WriteTarState state;
 	bbstreamer *manifest_inject_streamer;
 	bool		is_recovery_guc_supported;
+	bool		expect_unterminated_tarfile;
 
 	/* Pass all COPY data through to the backup streamer. */
 	memset(&state, 0, sizeof(state));
 	is_recovery_guc_supported =
 		PQserverVersion(conn) >= MINIMUM_VERSION_FOR_RECOVERY_GUC;
+	expect_unterminated_tarfile =
+		PQserverVersion(conn) < MINIMUM_VERSION_FOR_TERMINATED_TARFILE;
 	state.streamer = CreateBackupStreamer(archive_name, spclocation,
 										  &manifest_inject_streamer,
-										  is_recovery_guc_supported);
+										  is_recovery_guc_supported,
+										  expect_unterminated_tarfile);
 	state.tablespacenum = tablespacenum;
 	ReceiveCopyData(conn, ReceiveTarCopyChunk, &state);
 	progress_filename = NULL;