diff --git a/mixer/backend/sqlalchemy.py b/mixer/backend/sqlalchemy.py
index 4ad4e4c..8ff0fd1 100644
--- a/mixer/backend/sqlalchemy.py
+++ b/mixer/backend/sqlalchemy.py
@@ -222,6 +222,12 @@ def make_fabric(self, column, field_name=None, fake=False, kwargs=None): # noqa
         # don't directly inherit from the base types
         if TypeDecorator in ftype.__bases__:
             ftype = ftype.impl
+            # In SQLAlchemy within the TypeDecorator class in SQLAlchemy,
+            # the impl attribute is meant to reference a SQLAlchemy TypeEngine class
+            # or a pre-configured instance of such a class that corresponds with the database column type to be used.
+            # The TypeDecorator then extends or modifies the behavior of this type. 
+            if not inspect.isclass(ftype):
+                ftype = type(ftype)           
 
         stype = self.__factory.cls_to_simple(ftype)