diff --git a/_extensions/gdscript.py b/_extensions/gdscript.py
index d84312bfb..f00728e32 100644
--- a/_extensions/gdscript.py
+++ b/_extensions/gdscript.py
@@ -339,7 +339,7 @@ class GDScriptLexer(RegexLexer):
 
 
 def setup(sphinx):
-    sphinx.add_lexer("gdscript", GDScriptLexer)
+    sphinx.add_lexer("gdscript", GDScriptLexer())
 
     return {
         "parallel_read_safe": True,