diff --git a/django/template/loader.py b/django/template/loader.py
index 3fe47738942..c62c3833228 100644
--- a/django/template/loader.py
+++ b/django/template/loader.py
@@ -37,6 +37,12 @@ def find_template_loader(loader):
         if hasattr(TemplateLoader, 'load_template_source'):
             func = TemplateLoader(*args)
         else:
+            warnings.warn(
+                "Function-based template loaders are deprecated. Please use "
+                "class-based template loaders instead. Inherit base.Loader "
+                "and provide a load_template_source() method.",
+                RemovedInDjango20Warning, stacklevel=2)
+
             # Try loading module the old way - string is full path to callable
             if args:
                 raise ImproperlyConfigured(
diff --git a/docs/internals/deprecation.txt b/docs/internals/deprecation.txt
index 666ff1f492a..7247e4a2aad 100644
--- a/docs/internals/deprecation.txt
+++ b/docs/internals/deprecation.txt
@@ -85,6 +85,8 @@ details on these changes.
 * The backwards compatibility alias ``django.template.loader.BaseLoader`` will
   be removed.
 
+* Support for function-based template loaders will be removed.
+
 .. _deprecation-removed-in-1.9:
 
 1.9
diff --git a/docs/releases/1.8.txt b/docs/releases/1.8.txt
index 73c0e7a040d..d55ed1820d7 100644
--- a/docs/releases/1.8.txt
+++ b/docs/releases/1.8.txt
@@ -1040,6 +1040,13 @@ class decorators. As a consequence, when overriding ``setUpClass()`` or
 ``django.template.loaders.base.Loader``. If you've written a custom template
 loader that inherits ``BaseLoader``, you must inherit ``Loader`` instead.
 
+Function-based template loaders
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In addition to the documented class-based API for custom template loaders,
+Django still supported to some extent an earlier function-based API. This
+private API wasn't maintained or tested. Now it's formally deprecated.
+
 ``django.test.utils.TestTemplateLoader``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~