upgrading byte enums to c++17

Question

I have a codebase with byte defined like so:

typedef unsigned char byte;

And this enum:

enum SymbolTypes
{
    VARIABLE_SYMBOL_TYPE = 0,
    IDENTIFIER_SYMBOL_TYPE = 1,
    STR_CONSTANT_SYMBOL_TYPE = 2,
    INT_CONSTANT_SYMBOL_TYPE = 3,
    FLOAT_CONSTANT_SYMBOL_TYPE = 4,
    UNDEFINED_SYMBOL_TYPE = 5
};

At some point there is a comparison between a byte value and a member of this enum:

byte symbol_type = 0;
...
bool is_variable() { return (symbol_type == VARIABLE_SYMBOL_TYPE); }

When setting the compiler to use C++17, I get these errors:

error: reference to ‘byte’ is ambiguous

So I figured that maybe I'm supposed to be using std::byte now. After changing symbol_type to a std::byte, there is a new compiler error telling me that there's no operator == that matches the operands of std::byte and SymbolTypes. This SO answer says we can use an underlying type of std::byte like so:

enum SymbolTypes : std::underlying_type_t<std::byte>
{
    VARIABLE_SYMBOL_TYPE = 0,
    IDENTIFIER_SYMBOL_TYPE = 1,
    STR_CONSTANT_SYMBOL_TYPE = 2,
    INT_CONSTANT_SYMBOL_TYPE = 3,
    FLOAT_CONSTANT_SYMBOL_TYPE = 4,
    UNDEFINED_SYMBOL_TYPE = 5
};

However, the compiler still complains that there's no == operator with operands of type std::byte and SymbolTypes. How do I get this simple comparison line to compile correctly? Or should I be doing something else to avoid the usage of std::byte?