Index: compat.c
--- compat.c.orig	2020-06-16 16:46:28.000000000 +0200
+++ compat.c	2020-06-20 09:52:37.279096000 +0200
@@ -495,19 +495,21 @@
 		rprintf(FINFO, "(%s) Protocol versions: remote=%d, negotiated=%d\n",
 			am_server? "Server" : "Client", remote_protocol, protocol_version);
 	}
-	if (remote_protocol < MIN_PROTOCOL_VERSION
-	 || remote_protocol > MAX_PROTOCOL_VERSION) {
+	if (   ( am_server && (remote_protocol < MIN_CLIENT_PROTOCOL_VERSION || remote_protocol > MAX_CLIENT_PROTOCOL_VERSION))
+	    || (!am_server && (remote_protocol < MIN_SERVER_PROTOCOL_VERSION || remote_protocol > MAX_SERVER_PROTOCOL_VERSION))) {
 		rprintf(FERROR,"protocol version mismatch -- is your shell clean?\n");
 		rprintf(FERROR,"(see the rsync man page for an explanation)\n");
 		exit_cleanup(RERR_PROTOCOL);
 	}
-	if (remote_protocol < OLD_PROTOCOL_VERSION) {
-		rprintf(FINFO,"%s is very old version of rsync, upgrade recommended.\n",
-			am_server? "Client" : "Server");
+	if (   ( am_server && remote_protocol < OLD_CLIENT_PROTOCOL_VERSION)
+	    || (!am_server && remote_protocol < OLD_SERVER_PROTOCOL_VERSION)) {
+		rprintf(FINFO,"%s is very old version (protocol %d) of rsync, upgrade recommended.\n",
+			am_server? "Client" : "Server", remote_protocol);
 	}
-	if (protocol_version < MIN_PROTOCOL_VERSION) {
+	if (   ( am_server && protocol_version < MIN_SERVER_PROTOCOL_VERSION)
+	    || (!am_server && protocol_version < MIN_CLIENT_PROTOCOL_VERSION)) {
 		rprintf(FERROR, "--protocol must be at least %d on the %s.\n",
-			MIN_PROTOCOL_VERSION, am_server? "Server" : "Client");
+			am_server ? MIN_SERVER_PROTOCOL_VERSION : MIN_CLIENT_PROTOCOL_VERSION, am_server? "Server" : "Client");
 		exit_cleanup(RERR_PROTOCOL);
 	}
 	if (protocol_version > PROTOCOL_VERSION) {
Index: rsync.h
--- rsync.h.orig	2020-06-13 20:47:08.000000000 +0200
+++ rsync.h	2020-06-20 09:52:37.279320000 +0200
@@ -132,9 +132,12 @@
  * unlikely to begin by sending a byte between MIN_PROTOCL_VERSION and
  * MAX_PROTOCOL_VERSION. */
 
-#define MIN_PROTOCOL_VERSION 20
-#define OLD_PROTOCOL_VERSION 25
-#define MAX_PROTOCOL_VERSION 40
+#define MIN_SERVER_PROTOCOL_VERSION 20
+#define OLD_SERVER_PROTOCOL_VERSION 25
+#define MAX_SERVER_PROTOCOL_VERSION 40
+#define MIN_CLIENT_PROTOCOL_VERSION 25
+#define OLD_CLIENT_PROTOCOL_VERSION 27
+#define MAX_CLIENT_PROTOCOL_VERSION 40
 
 #define MIN_FILECNT_LOOKAHEAD 1000
 #define MAX_FILECNT_LOOKAHEAD 10000
Index: simd-checksum-x86_64.cpp
--- simd-checksum-x86_64.cpp.orig	2020-06-18 22:20:44.000000000 +0200
+++ simd-checksum-x86_64.cpp	2020-06-20 10:09:46.916109000 +0200
@@ -61,7 +61,7 @@
 #include <immintrin.h>
 
 /* Some clang versions don't like it when you use static with multi-versioned functions: linker errors */
-#ifdef __clang__
+#if 1
 #define MVSTATIC
 #else
 #define MVSTATIC static