diff --git a/src/basic/parse-util.c b/src/basic/parse-util.c
index dc868c9b8e..0430e33e40 100644
--- a/src/basic/parse-util.c
+++ b/src/basic/parse-util.c
@@ -123,8 +123,7 @@ int parse_ifindex(const char *s) {
 }
 
 int parse_mtu(int family, const char *s, uint32_t *ret) {
-        uint64_t u;
-        size_t m;
+        uint64_t u, m;
         int r;
 
         r = parse_size(s, 1024, &u);
@@ -134,10 +133,16 @@ int parse_mtu(int family, const char *s, uint32_t *ret) {
         if (u > UINT32_MAX)
                 return -ERANGE;
 
-        if (family == AF_INET6)
+        switch (family) {
+        case AF_INET:
+                m = IPV4_MIN_MTU; /* This is 68 */
+                break;
+        case AF_INET6:
                 m = IPV6_MIN_MTU; /* This is 1280 */
-        else
-                m = IPV4_MIN_MTU; /* For all other protocols, including 'unspecified' we assume the IPv4 minimal MTU */
+                break;
+        default:
+                m = 0;
+        }
 
         if (u < m)
                 return -ERANGE;
diff --git a/src/test/test-parse-util.c b/src/test/test-parse-util.c
index 7a485f390f..58d22b6cfe 100644
--- a/src/test/test-parse-util.c
+++ b/src/test/test-parse-util.c
@@ -914,15 +914,30 @@ TEST(parse_mtu) {
         assert_se(parse_mtu(AF_UNSPEC, "4294967295", &mtu) >= 0 && mtu == 4294967295);
         assert_se(parse_mtu(AF_UNSPEC, "500", &mtu) >= 0 && mtu == 500);
         assert_se(parse_mtu(AF_UNSPEC, "1280", &mtu) >= 0 && mtu == 1280);
+        assert_se(parse_mtu(AF_UNSPEC, "4294967296", &mtu) == -ERANGE);
+        assert_se(parse_mtu(AF_UNSPEC, "68", &mtu) >= 0 && mtu == 68);
+        assert_se(parse_mtu(AF_UNSPEC, "67", &mtu) >= 0 && mtu == 67);
+        assert_se(parse_mtu(AF_UNSPEC, "0", &mtu) >= 0 && mtu == 0);
+        assert_se(parse_mtu(AF_UNSPEC, "", &mtu) == -EINVAL);
+
+        assert_se(parse_mtu(AF_INET, "1500", &mtu) >= 0 && mtu == 1500);
+        assert_se(parse_mtu(AF_INET, "1400", &mtu) >= 0 && mtu == 1400);
+        assert_se(parse_mtu(AF_INET, "65535", &mtu) >= 0 && mtu == 65535);
+        assert_se(parse_mtu(AF_INET, "65536", &mtu) >= 0 && mtu == 65536);
+        assert_se(parse_mtu(AF_INET, "4294967295", &mtu) >= 0 && mtu == 4294967295);
+        assert_se(parse_mtu(AF_INET, "500", &mtu) >= 0 && mtu == 500);
+        assert_se(parse_mtu(AF_INET, "1280", &mtu) >= 0 && mtu == 1280);
+        assert_se(parse_mtu(AF_INET, "4294967296", &mtu) == -ERANGE);
+        assert_se(parse_mtu(AF_INET, "68", &mtu) >= 0 && mtu == 68);
+        assert_se(parse_mtu(AF_INET, "67", &mtu) == -ERANGE);
+        assert_se(parse_mtu(AF_INET, "0", &mtu) == -ERANGE);
+        assert_se(parse_mtu(AF_INET, "", &mtu) == -EINVAL);
+
         assert_se(parse_mtu(AF_INET6, "1280", &mtu) >= 0 && mtu == 1280);
         assert_se(parse_mtu(AF_INET6, "1279", &mtu) == -ERANGE);
-        assert_se(parse_mtu(AF_UNSPEC, "4294967296", &mtu) == -ERANGE);
         assert_se(parse_mtu(AF_INET6, "4294967296", &mtu) == -ERANGE);
         assert_se(parse_mtu(AF_INET6, "68", &mtu) == -ERANGE);
-        assert_se(parse_mtu(AF_UNSPEC, "68", &mtu) >= 0 && mtu == 68);
-        assert_se(parse_mtu(AF_UNSPEC, "67", &mtu) == -ERANGE);
-        assert_se(parse_mtu(AF_UNSPEC, "0", &mtu) == -ERANGE);
-        assert_se(parse_mtu(AF_UNSPEC, "", &mtu) == -EINVAL);
+        assert_se(parse_mtu(AF_INET6, "", &mtu) == -EINVAL);
 }
 
 TEST(parse_loadavg_fixed_point) {
diff --git a/test/test-network-generator-conversion.sh b/test/test-network-generator-conversion.sh
index 6224a4d04f..9a4732c981 100755
--- a/test/test-network-generator-conversion.sh
+++ b/test/test-network-generator-conversion.sh
@@ -296,7 +296,7 @@ INVALID_COMMAND_LINES=(
     "ip=10.0.0.1:::255.255.255::foo99:off"
     "ip=10.0.0.1:::255.255.255.0:invalid_hostname:foo99:off"
     "ip=10.0.0.1:::255.255.255.0::verylonginterfacename:off"
-    "ip=:::::dhcp99:dhcp6:0"
+    "ip=:::::dhcp99:dhcp6:4294967296"
     "ip=:::::dhcp99:dhcp6:-1"
     "ip=:::::dhcp99:dhcp6:666:52:54:00"
     "ip=fdef:c400:bd01:1096::2::[fdef:c400:bd01:1096::1]:64::ipv6:off:[fdef:c400:bd01:1096::aaaa]"