diff --git a/src/ftp.c b/src/ftp.c
index 29c970e..a8a1671 100644
--- a/src/ftp.c
+++ b/src/ftp.c
@@ -38,7 +38,7 @@ int ftplogin(struct clientparam *param, char *nbuf, int *innbuf) {
 	if(i < 3) return 706;
 	buf[i] = 0;
 	if(atoi(buf)/100 != 2) {
-		*innbuf = i;
+		if(innbuf)*innbuf = i;
 		return 702;
 	}
 	sprintf(buf, "USER %.128s\r\n", *param->extusername?param->extusername:(unsigned char *)"anonymous");
@@ -74,6 +74,9 @@ int ftplogin(struct clientparam *param, char *nbuf, int *innbuf) {
 			return 701;
 		}
 	}
+	/* USER answered at once, logged in (230) or refused: that answer is
+	   the client's, waiting for one to its PASS */
+	else if(innbuf)*innbuf = i;
 	if(res != 2) {
 		return 700;
 	}
diff --git a/tests/cases/ftppr.py b/tests/cases/ftppr.py
new file mode 100644
index 0000000..0fd9837
--- /dev/null
+++ b/tests/cases/ftppr.py
@@ -0,0 +1,106 @@
+"""The FTP proxy logging in to its server: whatever the server answers the
+login with reaches the client, which waits for the answer to its PASS."""
+
+import socket
+import threading
+
+# what the server answers USER with, and PASS if it asks for one
+LOGINS = {
+    "230 to USER": ([b"230 Anonymous user logged in"], None),
+    "multiline 230 to USER": ([b"230-Welcome", b"230-to the server", b"230 Login successful."], None),
+    "331 to USER, 230 to PASS": ([b"331 Please specify the password."], [b"230 Login successful."]),
+    "530 to USER": ([b"530 Not allowed here"], None),
+    "331 to USER, 530 to PASS": ([b"331 Please specify the password."], [b"530 Login incorrect."]),
+}
+
+
+def ftp_server(listener, user, password):
+    """Greets, answers the login as told, then NOOP and QUIT."""
+    while True:
+        try:
+            c, _ = listener.accept()
+        except OSError:
+            return
+        try:
+            f = c.makefile("rb")
+            c.sendall(b"220 Fake FTP\r\n")
+            if not f.readline().upper().startswith(b"USER "):
+                continue
+            c.sendall(b"".join(line + b"\r\n" for line in user))
+            if password is not None:
+                if not f.readline().upper().startswith(b"PASS "):
+                    continue
+                c.sendall(b"".join(line + b"\r\n" for line in password))
+            for line in f:
+                if line.upper().startswith(b"NOOP"):
+                    c.sendall(b"200 NOOP ok\r\n")
+                elif line.upper().startswith(b"QUIT"):
+                    c.sendall(b"221 Bye\r\n")
+                    break
+                else:
+                    c.sendall(b"502 Not implemented\r\n")
+        except OSError:
+            pass
+        finally:
+            c.close()
+
+
+def reply(f):
+    """The last line of a reply, multiline or not; empty at the end or on a
+    time out."""
+    while True:
+        try:
+            line = f.readline()
+        except OSError:
+            return b""
+        if not line:
+            return b""
+        if len(line) < 4 or line[3:4] != b"-":
+            return line.rstrip()
+
+
+def run(t):
+    servers = {}
+    for name, (user, password) in LOGINS.items():
+        listener = socket.socket()
+        listener.bind(("127.0.0.1", 0))
+        listener.listen(5)
+        threading.Thread(target=ftp_server, args=(listener, user, password), daemon=True).start()
+        servers[name] = listener
+
+    port = t.free_port()
+    t.start("ftppr", f"""
+        log
+        auth none
+        ftppr -p{port}
+    """, ports=[port])
+
+    # without WITH_FTP the service closes the connection at once
+    s = socket.create_connection(("127.0.0.1", port), timeout=5)
+    built = reply(s.makefile("rb"))
+    s.close()
+    if not built:
+        t.skip("the FTP proxy (not built in this configuration)")
+        for listener in servers.values():
+            listener.close()
+        t.stop_all()
+        return
+
+    for name, listener in servers.items():
+        s = socket.create_connection(("127.0.0.1", port), timeout=5)
+        f = s.makefile("rb")
+        reply(f)
+        s.sendall(b"USER anonymous@127.0.0.1:%d\r\n" % listener.getsockname()[1])
+        reply(f)
+        s.sendall(b"PASS test@example.com\r\n")
+        got = reply(f)
+        ok = LOGINS[name][1] if LOGINS[name][1] is not None else LOGINS[name][0]
+        t.eq(ok[-1][:3], got[:3], f"{name}: the client gets the server's answer")
+        if got.startswith(b"230"):
+            s.sendall(b"NOOP\r\n")
+            t.eq(b"200", reply(f)[:3], f"{name}: and the session goes on")
+        s.close()
+
+    for listener in servers.values():
+        listener.close()
+    t.stop_all()