Can realloc fail when shrinking buffer?

Question

Is it possible that realloc fails, when the new size is smaller than the old size of the buffer? In this example the buffer is resized from 100 to 50 bytes.

#include <stdlib.h>
#include <stdio.h>

int main(int, char**)
{
    void* b,* a;

    a = malloc(100);

    if(!a)  return 1;

    b = realloc(a, 50);

    if(!b)
    {
        puts("Is this reachable?");
        free(a);
        return 1;
    }

    free(b);

    return 0;
}