diff --git a/src/labthings/extensions.py b/src/labthings/extensions.py
index 81384283..4861f998 100644
--- a/src/labthings/extensions.py
+++ b/src/labthings/extensions.py
@@ -3,6 +3,7 @@
 import os
 import sys
 import traceback
+import inspect
 from importlib import util
 from typing import Callable, Dict, List, Union
 
@@ -269,15 +270,26 @@ def find_extensions_in_file(extension_path: str, module_name="extensions") -> li
     else:
         # TODO: Add documentation links to warnings
         if hasattr(mod, "LABTHINGS_EXTENSIONS"):
-            return [
-                ext_class()
-                for ext_class in getattr(mod, "LABTHINGS_EXTENSIONS")
-                if issubclass(ext_class, BaseExtension)
-            ]
+            ext_objects = []
+            for ext_element in getattr(mod, "LABTHINGS_EXTENSIONS"):
+                if inspect.isclass(ext_element) and issubclass(
+                    ext_element, BaseExtension
+                ):
+                    ext_objects.append(ext_element())
+                elif isinstance(ext_element, BaseExtension):
+                    logging.warning(
+                        "%s: Extension instance passed instead of class. LABTHINGS_EXTENSIONS should contain classes, not instances.",
+                        ext_element,
+                    )
+                    ext_objects.append(ext_element)
+                else:
+                    logging.error(
+                        "Unsupported extension type %s. Skipping.", type(ext_element)
+                    )
+            return ext_objects
         elif hasattr(mod, "__extensions__"):
             logging.warning(
-                "Explicit extension list using the __extensions__ global is deprecated.",
-                "Please use LABTHINGS_EXTENSIONS instead.",
+                "Explicit extension list using the __extensions__ global is deprecated. Please use LABTHINGS_EXTENSIONS instead."
             )
             return [
                 getattr(mod, ext_name) for ext_name in getattr(mod, "__extensions__")