GCC 4.7.1 Generalized Constant Expression Problem with Overload

I am trying to make a selection of a compilation algorithm using specialized specialization.

I am using the following code:

template <class C>
    struct choose
    { 
        typedef size_t (*type)(const C*);
        static constexpr type value = java_string_hashcode<C>;
    };

I specialized this structure for type char:

template <>
    struct choose<char>
    { 
        typedef size_t (*type)(const char*);
        static constexpr type value = fnv_1a_32_hash;
    };

But when I try to compile it, I get the following error with GCC 4.7.1:

error: field initializer is not constant

I think the problem is that the function is fnv_1a_32_hashoverloaded, even if the IMO implicit cast to size_t (*)(const char*)should solve this problem.

I finally found a workaround by renaming the overload or just by selecting the destination:

static constexpr type value = (type)fnv_1a_32_hash;

My question is : is this a compiler error? Or am I missing something? Please explain and specify specifications where necessary.

fnv_1a_32_hash implementation details:

constexpr size_t fnv_1a_32_hash(const char* p, size_t h) noexcept
{ 
    return (*p == 0) ? h : fnv_1a_32_hash(p + 1, (h ^ *p) * fnv::prime);
} 

constexpr size_t fnv_1a_32_hash(const char* p) noexcept
{ 
    return fnv_1a_32_hash(p, fnv::offset_basis);
}