diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 1491eecb0f..c79dfbeba2 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -46,8 +46,7 @@ typedef struct
 	char		nuls[2];		/* always \0\0 */
 	uint16		len;			/* size of this chunk (counts data only) */
 	int32		pid;			/* writer's pid */
-	char		is_last;		/* last chunk of message? 't' or 'f' ('T' or
-								 * 'F' for CSV case) */
+	bits8		flags;			/* bitmask of PIPE_PROTO_* */
 	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data payload starts here */
 } PipeProtoHeader;
 
@@ -60,6 +59,11 @@ typedef union
 #define PIPE_HEADER_SIZE  offsetof(PipeProtoHeader, data)
 #define PIPE_MAX_PAYLOAD  ((int) (PIPE_CHUNK_SIZE - PIPE_HEADER_SIZE))
 
+/* flag bits for PipeProtoHeader->flags */
+#define PIPE_PROTO_IS_LAST	0x01	/* last chunk of message? */
+/* log destinations */
+#define PIPE_PROTO_DEST_STDERR	0x10
+#define PIPE_PROTO_DEST_CSVLOG	0x20
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index cad43bdef2..c00b2dc186 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -891,8 +891,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
-			(p.is_last == 't' || p.is_last == 'f' ||
-			 p.is_last == 'T' || p.is_last == 'F'))
+			(p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG)) != 0)
 		{
 			List	   *buffer_list;
 			ListCell   *cell;
@@ -906,8 +905,15 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 			if (count < chunklen)
 				break;
 
-			dest = (p.is_last == 'T' || p.is_last == 'F') ?
-				LOG_DESTINATION_CSVLOG : LOG_DESTINATION_STDERR;
+			if ((p.flags & PIPE_PROTO_DEST_STDERR) != 0)
+				dest = LOG_DESTINATION_STDERR;
+			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
+				dest = LOG_DESTINATION_CSVLOG;
+			else
+			{
+				/* this should never happen as of the header validation */
+				Assert(false);
+			}
 
 			/* Locate any existing buffer for this source pid */
 			buffer_list = buffer_lists[p.pid % NBUFFER_LISTS];
@@ -924,7 +930,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 					free_slot = buf;
 			}
 
-			if (p.is_last == 'f' || p.is_last == 'F')
+			if ((p.flags & PIPE_PROTO_IS_LAST) == 0)
 			{
 				/*
 				 * Save a complete non-final chunk in a per-pid buffer
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 816b071afa..2af87ee3bd 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3250,11 +3250,16 @@ write_pipe_chunks(char *data, int len, int dest)
 
 	p.proto.nuls[0] = p.proto.nuls[1] = '\0';
 	p.proto.pid = MyProcPid;
+	p.proto.flags = 0;
+	if (dest == LOG_DESTINATION_STDERR)
+		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
+	else if (dest == LOG_DESTINATION_CSVLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
 	{
-		p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'F' : 'f');
+		/* no need to set PIPE_PROTO_IS_LAST yet */
 		p.proto.len = PIPE_MAX_PAYLOAD;
 		memcpy(p.proto.data, data, PIPE_MAX_PAYLOAD);
 		rc = write(fd, &p, PIPE_HEADER_SIZE + PIPE_MAX_PAYLOAD);
@@ -3264,7 +3269,7 @@ write_pipe_chunks(char *data, int len, int dest)
 	}
 
 	/* write the last chunk */
-	p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'T' : 't');
+	p.proto.flags |= PIPE_PROTO_IS_LAST;
 	p.proto.len = len;
 	memcpy(p.proto.data, data, len);
 	rc = write(fd, &p, PIPE_HEADER_SIZE + len);