diff --git a/pscp.c b/pscp.c
index 8693668f..ab3077bd 100644
--- a/pscp.c
+++ b/pscp.c
@@ -50,6 +50,8 @@ static void source(char *src);
 static void rsource(char *src);
 static void sink(char *targ, char *src);
 
+const char *const appname = "PSCP";
+
 /*
  * The maximum amount of queued data we accept before we stop and
  * wait for the server to process some.
diff --git a/psftp.c b/psftp.c
index fe01b1a9..e0fbee8d 100644
--- a/psftp.c
+++ b/psftp.c
@@ -16,6 +16,8 @@
 #include "sftp.h"
 #include "int64.h"
 
+const char *const appname = "PSFTP";
+
 /*
  * Since SFTP is a request-response oriented protocol, it requires
  * no buffer management: when we send data, we stop and wait for an
diff --git a/x11fwd.c b/x11fwd.c
index ba76f782..d674120a 100644
--- a/x11fwd.c
+++ b/x11fwd.c
@@ -712,7 +712,7 @@ int x11_send(Socket s, char *data, int len)
 	    int msglen, msgsize;
 	    unsigned char *reply;
 
-	    message = dupprintf("PuTTY X11 proxy: %s", err);
+	    message = dupprintf("%s X11 proxy: %s", appname, err);
 	    msglen = strlen(message);
 	    reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
 	    msgsize = (msglen + 3) & ~3;