I have a doubt.

Borel computed the rank of the higher algebraic k-theory of $\mathbb{Z}$:

$rank(K_n)(\mathbb{Z})= 1$ if $n\equiv1 mod4$, otherwise this rank is equal to 0.

On the other hand Bjorn Jahren proved for any finite group $G$ that

$rank(K_n(\mathbb{Z}[G]))=c$ if $n\equiv3 mod4$, where c is the number of irreductible complex representation of G.

If I let $G=1$, then I have that $rank(K_n)(\mathbb{Z})= 1$ if $n\equiv3 mod4$...

this is a contradiction with Borel's result. What happened here? Am I wrong? (I hope so)