Default parameter in template -> template argument involves template parameter

I have a problem similar to this one: SFINAE tried with bool gives compiler error: "template argument ‘T::value’ involves template parameter"

I want to define a trait that tells if a complex representation is an array of structs, where real values are never AoS hence no user defined specilization should be required, but for complex you'd always need one:

/**
 * Evaluates to a true type if the given complex type is an Array of Structs, false otherwise
 * Defaults to false for Real values
 */
template< typename T, bool T_isComplex = IsComplex<T>::value >
struct IsAoS: std::false_type{};

/**
 * Undefined for (unknown) complex types
 */
template< typename T >
struct IsAoS< T, true >;

Specializations are done in the std-way by deriving from std::true/false_type.

The problem is: With this implementation I get the "template argument involves template parameter(s)" error (which is explained in the linked question) but if i switch to types (ommit "::value" in first template and change true to true_type in 2nd) Complex types won't match the 2nd template anymore because the only derive from std::true_type and ARE NOT std::true_type.

Only solution I can think of is using expression SFINAE and change the 2nd parameter of the main template to default void and an enable_if for the real case (isComplex==false). Anything better?