diff --git a/doc/manual/source/the-model-file.rst b/doc/manual/source/the-model-file.rst
index 16babc48f1e577e76c27169595c06f60986bb0b8..bf8608f1be0372cc45a55b3b2ac8263af01eea29 100644
--- a/doc/manual/source/the-model-file.rst
+++ b/doc/manual/source/the-model-file.rst
@@ -13673,9 +13673,9 @@ More generally, it is possible to consider finite discounted sums.
 
     Name of the associated auxiliary model, defined with ``var_model`` or ``trend_component_model``.
 
-    .. option:: expression = STRING | QUOTED_STRING
+    .. option:: expression = VARIABLE_NAME | EXPRESSION
 
-    Name of the variable or expression (linear combination of variables) to be expected. The quotes are mandatory if an expression is expected.
+    Name of the variable or expression (linear combination of variables) to be expected.
 
     .. option:: discount = PARAMETER_NAME | DOUBLE