diff --git a/doc/changelog.d/5050.fixed.md b/doc/changelog.d/5050.fixed.md
new file mode 100644
index 00000000000..302054a5d53
--- /dev/null
+++ b/doc/changelog.d/5050.fixed.md
@@ -0,0 +1 @@
+Invalid state and TypeError bug in \`_AllowedDomainNames.valid_name\`
diff --git a/src/ansys/fluent/core/services/solution_variables.py b/src/ansys/fluent/core/services/solution_variables.py
index 655bef2f5b8..68c544376e9 100644
--- a/src/ansys/fluent/core/services/solution_variables.py
+++ b/src/ansys/fluent/core/services/solution_variables.py
@@ -327,6 +327,19 @@ def __init__(self, zone_name: str, allowed_values: List[str]):
         )
 
 
+class DomainError(ValueError):
+    """Exception class for errors in domain name."""
+
+    def __init__(self, domain_name: str, allowed_values: List[str]):
+        """Initialize DomainError."""
+        self.domain_name = domain_name
+        super().__init__(
+            allowed_name_error_message(
+                context="domain", trial_name=domain_name, allowed_values=allowed_values
+            )
+        )
+
+
 class _AllowedNames:
     def is_valid(self, name):
         """Check whether a given name is valid or not."""
@@ -422,15 +435,16 @@ def valid_name(self, domain_name):
 
         Raises
         ------
-        ZoneError
+        DomainError
             If the given domain name is invalid.
         """
-        if not self.is_valid(domain_name):
-            raise ZoneError(
-                domain_name=domain_name,
-                allowed_values=self(),
-            )
-        return self._zones_info.domain_id(domain_name)
+        domain_id = self._zones_info.domain_id(domain_name)
+        if domain_id is not None:
+            return domain_id
+        raise DomainError(
+            domain_name=domain_name,
+            allowed_values=self(),
+        )
 
 
 class _SvarMethod:
diff --git a/tests/test_solution_variables.py b/tests/test_solution_variables.py
index 37ca9c588c4..7a87952c7f0 100644
--- a/tests/test_solution_variables.py
+++ b/tests/test_solution_variables.py
@@ -25,9 +25,64 @@
 
 from ansys.fluent.core import examples
 from ansys.fluent.core.examples.downloads import download_file
+from ansys.fluent.core.services.solution_variables import (
+    DomainError,
+    _AllowedDomainNames,
+)
 from ansys.units.variable_descriptor import VariableCatalog
 
 
+class _DummyZonesInfo:
+    """Mock ZonesInfo for unit testing _AllowedDomainNames."""
+
+    def __init__(self, domains, domain_id_map):
+        self._domains = domains
+        self._domain_id_map = domain_id_map
+
+    @property
+    def domains(self):
+        return self._domains
+
+    def domain_id(self, name):
+        return self._domain_id_map.get(name, None)
+
+
+class _DummySVInfo:
+    """Mock SolutionVariableInfo for unit testing _AllowedDomainNames."""
+
+    def __init__(self, zones_info):
+        self._zones_info = zones_info
+
+    def get_zones_info(self):
+        return self._zones_info
+
+
+def test_allowed_domain_names_valid_name_returns_domain_id():
+    zones_info = _DummyZonesInfo(domains=["mixture"], domain_id_map={"mixture": 1})
+    allowed = _AllowedDomainNames(_DummySVInfo(zones_info))
+    assert allowed.valid_name("mixture") == 1
+
+
+def test_allowed_domain_names_valid_name_domain_id_zero():
+    zones_info = _DummyZonesInfo(domains=["mixture"], domain_id_map={"mixture": 0})
+    allowed = _AllowedDomainNames(_DummySVInfo(zones_info))
+    assert allowed.valid_name("mixture") == 0
+
+
+def test_allowed_domain_names_valid_name_raises_on_missing_domain_id():
+    zones_info = _DummyZonesInfo(domains=["mixture"], domain_id_map={})
+    allowed = _AllowedDomainNames(_DummySVInfo(zones_info))
+    with pytest.raises(DomainError):
+        allowed.valid_name("mixture")
+
+
+def test_allowed_domain_names_valid_name_raises_on_invalid_domain():
+    zones_info = _DummyZonesInfo(domains=["mixture"], domain_id_map={"mixture": 1})
+    allowed = _AllowedDomainNames(_DummySVInfo(zones_info))
+    with pytest.raises(DomainError):
+        allowed.valid_name("nonexistent")
+
+
 @pytest.mark.fluent_version(">=23.2")
 def test_solution_variables(new_solver_session):
     solver = new_solver_session