diff --git a/src/ytdl_sub/utils/scriptable.py b/src/ytdl_sub/utils/scriptable.py
index 4a136468..6aff1db3 100644
--- a/src/ytdl_sub/utils/scriptable.py
+++ b/src/ytdl_sub/utils/scriptable.py
@@ -15,7 +15,7 @@ from ytdl_sub.utils.exceptions import StringFormattingException
 from ytdl_sub.utils.script import ScriptUtils
 
 BASE_SCRIPT: Script = Script(
-    ScriptUtils.add_sanitized_variables(dict(VARIABLE_SCRIPTS, **CUSTOM_FUNCTION_SCRIPTS))
+    dict(ScriptUtils.add_sanitized_variables(VARIABLE_SCRIPTS), **CUSTOM_FUNCTION_SCRIPTS)
 )
 
 
diff --git a/src/ytdl_sub/validators/string_formatter_validators.py b/src/ytdl_sub/validators/string_formatter_validators.py
index 5c776d43..def6e6d8 100644
--- a/src/ytdl_sub/validators/string_formatter_validators.py
+++ b/src/ytdl_sub/validators/string_formatter_validators.py
@@ -173,7 +173,7 @@ def _validate_formatter(
         text=formatter_validator.format_string,
     )
     variable_names = {var.name for var in parsed.variables}
-    custom_function_names = {func.name for func in parsed.custom_functions}
+    custom_function_names = {f"%{func.name}" for func in parsed.custom_functions}
 
     if not variable_names.issubset(mock_script.variable_names):
         raise StringFormattingVariableNotFoundException(