Overcoherence implies holonomicity

Let $\V$ be a mixed characteristic complete discrete valuation ring with perfect residue field. Let $\X$ be a smooth formal scheme over $\V$. We prove than a $\D ^\dag_{\X,\Q} $-module which is overcoherent after any change of basis is an holonomic $\D ^\dag_{\X,\Q} $-module. Furthermore, we check that this implies than a bounded complex $\E$ of $\D ^\dag_{\X,\,\Q}$-modules is overholonomic after any change of basis if and only if, for any integer $j$, $\mathcal{H} ^{j} (\E) $ is overholonomic after any change of basis.