diff --git a/os_service_types/exc.py b/os_service_types/exc.py
index 0eff50f..ab6abb8 100644
--- a/os_service_types/exc.py
+++ b/os_service_types/exc.py
@@ -31,3 +31,11 @@ class AliasUsageWarning(Warning):
     Requested service_type {given} is an old alias. Please update your
     code to reference the official service_type {official}.
     """
+
+
+class UnofficialUsageWarning(Warning):
+    """Use of unofficial service-types is discouraged."""
+
+    details = """
+    Requested service_type {given} is not a known official OpenStack project.
+    """
diff --git a/os_service_types/service_types.py b/os_service_types/service_types.py
index 3a875f3..125403e 100644
--- a/os_service_types/service_types.py
+++ b/os_service_types/service_types.py
@@ -208,16 +208,24 @@ class ServiceTypes(object):
         service_type = _normalize_type(service_type)
         return self._service_types_data['forward'].get(service_type, [])
 
-    def get_service_type(self, service_type):
+    def get_service_type(self, service_type, permissive=False):
         """Given a possible service_type, return the official type.
 
         :param str service_type: A potential service-type.
+        :param bool permissive:
+            Return the original type if the given service_type is not found.
         :returns str: The official service-type, or None if there is no match.
         """
         service_type = _normalize_type(service_type)
         if self.is_official(service_type):
             return service_type
         official = self._service_types_data['reverse'].get(service_type)
+        if permissive and official is None:
+            if self._warn:
+                exc.warn(
+                    exc.UnofficialUsageWarning,
+                    given=service_type)
+            return service_type
         if self._warn:
             exc.warn(
                 exc.AliasUsageWarning, given=service_type, official=official)
diff --git a/os_service_types/tests/base.py b/os_service_types/tests/base.py
index 26ae512..731d152 100644
--- a/os_service_types/tests/base.py
+++ b/os_service_types/tests/base.py
@@ -118,6 +118,12 @@ class ServiceDataMixin(object):
             self.assertIsNone(
                 self.service_types.get_service_type(self.service_type))
 
+    def test_get_service_type_permissive(self):
+        self.assertEqual(
+            self.official or self.service_type,
+            self.service_types.get_service_type(
+                self.service_type, permissive=True))
+
     def test_get_aliases(self):
         self.assertEqual(
             self.aliases,