Why this code snippet works with C++17 whereas the compiler complains when using C++11?

Why this code snippet works with C++17 whereas the compiler complains when using C++11(i.e https://godbolt.org/z/71G91P)? Are there any potential problems with this code snippet?

#include<iostream>

class ctx
{
    public:
        int map_create(void*){std::cout << "haha" << std::endl; return 0;};
};

ctx obj;
typedef int (ctx::*ctx_mem_func)(void*);

template <ctx_mem_func func>
int regHelper(void*) 
{
    ((&obj)->*func)(nullptr);
    return 0;
}

constexpr ctx_mem_func testFunc = &ctx::map_create;

typedef int(*callBackFunc)(void*);

int reg(callBackFunc)
{
    return 0;
}

int main()
{
    reg(regHelper<testFunc>);
    //But this expression is ok.
    reg(regHelper<&ctx::map_create>);
    
    std::cout << "this is a test" << std::endl;
} 

Here are the error messages when using c++11(gun 10.0.2):

<source>: In function 'int main()':
<source>:30:28: error: no matches converting function 'regHelper' to type 'callBackFunc {aka int (*)(void*)}'
     reg(regHelper<testFunc>);
                            ^
<source>:13:5: note: candidate is: template<int (ctx::* func)(void*)> int regHelper(void*)
 int regHelper(void*) 
     ^