diff --git a/src/ytdl_sub/script/types/function.py b/src/ytdl_sub/script/types/function.py
index f8a6a862..c61e26b7 100644
--- a/src/ytdl_sub/script/types/function.py
+++ b/src/ytdl_sub/script/types/function.py
@@ -96,7 +96,7 @@ class CustomFunction(Function):
 
             resolved_variables_with_args = copy.deepcopy(resolved_variables)
             for i, arg in enumerate(resolved_args):
-                function_arg = FunctionArgument(name=f"${i}")  # Function args are 1-based
+                function_arg = FunctionArgument(name=f"${i}")  # Function args are 0-based
                 if function_arg in resolved_variables_with_args:
                     raise StringFormattingException("nested custom functions???")
                 resolved_variables_with_args[function_arg] = arg