diff --git a/src/components/simulation-chart.tsx b/src/components/simulation-chart.tsx
index 8465fd1..ee18e93 100644
--- a/src/components/simulation-chart.tsx
+++ b/src/components/simulation-chart.tsx
@@ -609,7 +609,7 @@ const SimulationChart = React.memo(({
                   style={{ stroke: isDarkTheme ? '#666' : '#ccc' }}
             />
 
-            {showDayReferenceLines !== false && [...Array(dispDays + 1).keys()].map(day => {
+            {showDayReferenceLines !== false && [...Array(simDays).keys()].map(day => {
               // Determine whether to use compact day labels to avoid overlap on narrow screens
               const pxPerDay = scrollableWidth / Math.max(1, dispDays);
               let label = "";