"strlen(s1) - strlen(s2)" is never less than zero

I am currently writing a C program that requires frequent comparisons of string lengths so I wrote the following helper function:

int strlonger(char *s1, char *s2) {
    return strlen(s1) - strlen(s2) > 0;
}

I have noticed that the function returns true even when s1 has shorter length than s2. Can someone please explain this strange behavior?