diff --git a/docs/sphinx/conf.py b/docs/sphinx/conf.py
index 2d04da5b..49fcec52 100644
--- a/docs/sphinx/conf.py
+++ b/docs/sphinx/conf.py
@@ -331,7 +331,7 @@ f.close()
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.autodoc', 'sphinx.ext.todo', 'sphinx.ext.imgmath', 'sphinx.ext.inheritance_diagram', 'sphinx.ext.graphviz', 'sphinx.ext.viewcode']
+extensions = ['sphinx.ext.autodoc', 'sphinx.ext.todo', 'sphinx.ext.pngmath', 'sphinx.ext.inheritance_diagram', 'sphinx.ext.graphviz', 'sphinx.ext.viewcode']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
diff --git a/waflib/Tools/waf_unit_test.py b/waflib/Tools/waf_unit_test.py
index 35219a72..754b9836 100644
--- a/waflib/Tools/waf_unit_test.py
+++ b/waflib/Tools/waf_unit_test.py
@@ -54,6 +54,10 @@ sys.exit(status)
 
 @taskgen_method
 def handle_ut_cwd(self, key):
+	"""
+	Task generator method, used internally to limit code duplication.
+	This method may disappear anytime.
+	"""
 	cwd = getattr(self, key, None)
 	if cwd:
 		if isinstance(cwd, str):