diff --git a/_extensions/gdscript.py b/_extensions/gdscript.py
index 11a8265e0..77aefc17c 100644
--- a/_extensions/gdscript.py
+++ b/_extensions/gdscript.py
@@ -341,7 +341,7 @@ class GDScriptLexer(RegexLexer):
 
 
 def setup(sphinx):
-    sphinx.add_lexer("gdscript", GDScriptLexer)
+    sphinx.add_lexer("gdscript", GDScriptLexer())
 
     return {
         "parallel_read_safe": True,