diff --git a/doc/share/conf.py b/doc/share/conf.py
index 9abc20b..7c68a4e 100644
--- a/doc/share/conf.py
+++ b/doc/share/conf.py
@@ -99,5 +99,5 @@ def get_version():
 
 
 def setup(app):
-    app.add_lexer('ada', ada_pygments.AdaLexer())
-    app.add_lexer('gpr', ada_pygments.GNATProjectLexer())
+    app.add_lexer('ada', ada_pygments.AdaLexer)
+    app.add_lexer('gpr', ada_pygments.GNATProjectLexer)