diff --git a/common/test/run-ip_port_parsing.c b/common/test/run-ip_port_parsing.c
index 13d34952c50b..a35fdfa749e1 100644
--- a/common/test/run-ip_port_parsing.c
+++ b/common/test/run-ip_port_parsing.c
@@ -150,7 +150,18 @@ int main(int argc, char *argv[])
 	assert(!separate_address_and_port(tmpctx, "[::1]:8f", &ip, &port));
 	assert(!separate_address_and_port(tmpctx, "127.0.0.1:8f", &ip, &port));
 	assert(!separate_address_and_port(tmpctx, "127.0.0.1:0", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:65536", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:65537", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:75271", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:99999", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:18446744073709551616", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:-1", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1:+9735", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "127.0.0.1: 9735", &ip, &port));
 	assert(!separate_address_and_port(tmpctx, "127.0.0.1:ff", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "[::1]:65536", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "[::1]:65537", &ip, &port));
+	assert(!separate_address_and_port(tmpctx, "[::1]:-1", &ip, &port));
 
 	/* ret = getaddrinfo("[::1]:80", NULL, NULL, &res); */
 	assert(separate_address_and_port(tmpctx, "[::1]:80", &ip, &port));
@@ -170,6 +181,10 @@ int main(int argc, char *argv[])
 	assert(streq(ip, "192.168.1.1"));
 	assert(port == 8000);
 
+	assert(separate_address_and_port(tmpctx, "127.0.0.1:65535", &ip, &port));
+	assert(streq(ip, "127.0.0.1"));
+	assert(port == 65535);
+
 	port = 0;
 	assert(separate_address_and_port(tmpctx, "192.168.2.255", &ip, &port));
 	assert(streq(ip, "192.168.2.255"));
diff --git a/common/wireaddr.c b/common/wireaddr.c
index 1364e4931383..ba7d5a2b4e15 100644
--- a/common/wireaddr.c
+++ b/common/wireaddr.c
@@ -344,9 +344,13 @@ bool separate_address_and_port(const tal_t *ctx, const char *arg,
 	}
 
 	if (portcolon) {
-		char *endp;
-		*port = strtol(portcolon + 1, &endp, 10);
-		return *port != 0 && *endp == '\0';
+		u64 p;
+		if (!str_to_u64(portcolon + 1, strlen(portcolon + 1), &p))
+			return false;
+		if (p == 0 || p > 65535)
+			return false;
+		*port = p;
+		return true;
 	}
 
 	return true;