diff --git a/frontend/app/portfolio/page.tsx b/frontend/app/portfolio/page.tsx
index e676326..d044be9 100644
--- a/frontend/app/portfolio/page.tsx
+++ b/frontend/app/portfolio/page.tsx
@@ -209,7 +209,7 @@ export default function PortfolioPage() {
                       <Cell key={`${entry.name}-${index}`} fill={CHART_COLORS[index % CHART_COLORS.length]} />
                     ))}
                   </Pie>
-                  <Tooltip formatter={(value: number) => formatCurrency(value)} />
+                  <Tooltip formatter={(value: number | string | undefined) => formatCurrency(value)} />
                 </PieChart>
               </ResponsiveContainer>
             </div>
@@ -228,7 +228,7 @@ export default function PortfolioPage() {
                   <CartesianGrid strokeDasharray="2 2" stroke="rgba(126, 217, 255, 0.2)" />
                   <XAxis dataKey="name" stroke="#8cb6c5" fontSize={12} />
                   <YAxis stroke="#8cb6c5" fontSize={12} />
-                  <Tooltip formatter={(value: number) => `${value.toFixed(2)}%`} />
+                  <Tooltip formatter={(value: number | string | undefined) => `${asNumber(value).toFixed(2)}%`} />
                   <Bar dataKey="value" fill="#68ffd5" radius={[4, 4, 0, 0]} />
                 </BarChart>
               </ResponsiveContainer>