Asking for input until it is valid in C

Question

I'm not asking for a solution but rather for an explanation.

I'd like to understand why this enters an infinite loop (printing "Escolha um ano" non-stop) if the input is invalid.

while(error)
{
   puts("Escolha um ano:");

   if(scanf(" %d", &ano)!= 1)
   {
      puts("Escolheu mal o ano. Tente de novo");
   }
   else error = 0;
}