diff --git a/komposer/types/cli.py b/komposer/types/cli.py
index 92d2927..83d96e9 100644
--- a/komposer/types/cli.py
+++ b/komposer/types/cli.py
@@ -7,17 +7,12 @@
 from komposer.types.base import ImmutableBaseModel
 from komposer.utils import load_yaml
 
-RFC_1123_MAX_LENGTH = 63
+lowercase_kebak_re = re.compile(r"^[a-z0-9][a-z\-0-9]*[a-z0-9]$")
 
-rfc_1123_re = re.compile(r"^[a-z][a-z\-0-9]*[a-z]$")
 
-
-def ensure_is_rfc_1123(string: str) -> None:
-    if not rfc_1123_re.match(string):
-        raise ValueError("Not a valid RFC-1123 string")
-
-    if len(string) > RFC_1123_MAX_LENGTH:
-        raise ValueError("String is longer than 63 characters")
+def ensure_lowercase_kebab(string: str) -> None:
+    if not lowercase_kebak_re.match(string):
+        raise ValueError("Not a lowercase kebab string")
 
 
 class DeploymentContext(ImmutableBaseModel):
@@ -50,19 +45,19 @@ class Context(ImmutableBaseModel):
 
     @validator("project_name")
     def project_name_matches_kubernetes_name(cls, value: str) -> str:
-        ensure_is_rfc_1123(value)
+        ensure_lowercase_kebab(value)
 
         return value
 
     @validator("branch_name")
     def branch_name_matches_kubernetes_name(cls, value: str) -> str:
-        ensure_is_rfc_1123(value)
+        ensure_lowercase_kebab(value)
 
         return value
 
     @validator("repository_name")
     def repository_name_matches_kubernetes_name(cls, value: str) -> str:
-        ensure_is_rfc_1123(value)
+        ensure_lowercase_kebab(value)
 
         return value
 
diff --git a/tests/core/base_test.py b/tests/core/base_test.py
index dd0ea82..8efd814 100644
--- a/tests/core/base_test.py
+++ b/tests/core/base_test.py
@@ -1,5 +1,5 @@
 from pathlib import Path
-from typing import Sequence
+from typing import Optional, Sequence
 
 import pytest
 from pytest_mock import MockerFixture
@@ -29,7 +29,7 @@
 from tests.fixtures import make_context, make_labels
 
 
-def make_minimal_docker_compose(ports: list[str] = None) -> docker_compose.DockerCompose:
+def make_minimal_docker_compose(ports: Optional[list[str]] = None) -> docker_compose.DockerCompose:
     return docker_compose.DockerCompose(
         services={"my-service": docker_compose.Service(ports=ports or [])}
     )
diff --git a/tests/types/cli_test.py b/tests/types/cli_test.py
index fa39f53..ef189b4 100644
--- a/tests/types/cli_test.py
+++ b/tests/types/cli_test.py
@@ -2,7 +2,7 @@
 
 import pytest
 
-from komposer.types.cli import ensure_is_rfc_1123
+from komposer.types.cli import ensure_lowercase_kebab
 from tests.fixtures import make_context
 
 
@@ -45,37 +45,34 @@ def test_context_manifest_prefix(
         pytest.param("string", id="Simple string"),
         pytest.param("my-string", id="String with hyphens"),
         pytest.param("my-1-string", id="String with digits"),
-        pytest.param("a" * 63, id="Max length of the string"),
+        pytest.param("1-string", id="String with leading digits"),
+        pytest.param("string-1", id="String with trailing digits"),
     ],
 )
 def test_ensure_is_kubernetes_name(value: str) -> None:
     """
     GIVEN a string
-        AND the string is a valid RFC 1123
+        AND the string is in lowercase kebab format
     WHEN calling ensure_is_kubernetes_name
     THEN no exception is raised
     """
-    ensure_is_rfc_1123(value)
+    ensure_lowercase_kebab(value)
 
 
 @pytest.mark.parametrize(
-    "value, expected",
+    "value",
     [
-        pytest.param("", "Not a valid RFC-1123 string", id="Empty string"),
-        pytest.param("1string", "Not a valid RFC-1123 string", id="String with leading digit"),
-        pytest.param("string1", "Not a valid RFC-1123 string", id="String with trailing digit"),
-        pytest.param(
-            "my/string", "Not a valid RFC-1123 string", id="String with unsupported symbol"
-        ),
-        pytest.param("a" * 64, "String is longer than 63 characters", id="String is too long"),
+        pytest.param("", id="Empty string"),
+        pytest.param("my/string", id="String with unsupported symbol /"),
+        pytest.param("my_string", id="String with unsupported symbol _"),
     ],
 )
-def test_ensure_is_kubernetes_name_fails_if_not_rfc_1123(value: str, expected: str) -> None:
+def test_ensure_is_kubernetes_name_fails_if_not_lowercase_kebak(value: str) -> None:
     """
     GIVEN a string
-        AND the string is not a valid RFC 1123
+        AND the string is not in lowercase kebab format
     WHEN calling ensure_is_kubernetes_name
     THEN an exception is raised
     """
-    with pytest.raises(ValueError, match=expected):
-        ensure_is_rfc_1123(value)
+    with pytest.raises(ValueError, match="Not a lowercase kebab string"):
+        ensure_lowercase_kebab(value)