diff --git a/cloudinit/sources/DataSourceOpenNebula.py b/cloudinit/sources/DataSourceOpenNebula.py
index 4c1401a952c..68db118a51d 100644
--- a/cloudinit/sources/DataSourceOpenNebula.py
+++ b/cloudinit/sources/DataSourceOpenNebula.py
@@ -302,7 +302,7 @@ def gen_conf(self) -> Dict[str, Any]:
             # Set MTU size
             mtu = self.get_mtu(c_dev)
             if mtu:
-                devconf["mtu"] = mtu
+                devconf["mtu"] = int(mtu)
 
             ethernets[dev] = devconf
 
diff --git a/tests/unittests/sources/test_opennebula.py b/tests/unittests/sources/test_opennebula.py
index a2f07baf27e..c7b4ea6b1db 100644
--- a/tests/unittests/sources/test_opennebula.py
+++ b/tests/unittests/sources/test_opennebula.py
@@ -789,7 +789,7 @@ def test_gen_conf_mtu(self, m_get_phys_by_mac):
                 "version": 2,
                 "ethernets": {
                     nic: {
-                        "mtu": "1280",
+                        "mtu": 1280,
                         "match": {"macaddress": MACADDR},
                         "addresses": [IP_BY_MACADDR + "/" + IP4_PREFIX],
                     }
@@ -898,7 +898,7 @@ def test_eth0_v4v6_override(self):
                             "addresses": ["1.2.3.6", "1.2.3.7", "1.2.3.8"],
                             "search": ["example.com", "example.org"],
                         },
-                        "mtu": "1280",
+                        "mtu": 1280,
                     }
                 },
             }
@@ -959,7 +959,7 @@ def test_multiple_nics(self):
                         "addresses": ["1.2.3.6", "1.2.3.7", "1.2.3.8"],
                         "search": ["example.com"],
                     },
-                    "mtu": "1280",
+                    "mtu": 1280,
                 },
                 "enp0s25": {
                     "match": {"macaddress": MAC_1},