diff --git a/src/lib/ChartUtils.ts b/src/lib/ChartUtils.ts
index de4cf94..746c0fa 100644
--- a/src/lib/ChartUtils.ts
+++ b/src/lib/ChartUtils.ts
@@ -43,7 +43,7 @@ export const ticks = (values: number[], opts: TickOptions = {}): number[] => {
     n += tickSpacing;
   }
   if (max > niceMax) result.push(n);
-  while (min < result[0]) result.unshift(result[0] - tickSpacing);
+  while (result[0] && min < result[0]) result.unshift(result[0] - tickSpacing);
 
   if (!result.length) {
     return [0, 100];
diff --git a/src/lib/Details.svelte b/src/lib/Details.svelte
index 47938eb..34ef8d5 100644
--- a/src/lib/Details.svelte
+++ b/src/lib/Details.svelte
@@ -67,7 +67,7 @@
     <List
       items={[
         { label: 'Speed', value: `${data.speed} ${units === 'metric' ? 'km/h' : 'mph'}`, color: ChartColours.Speed },
-        ...(data.erpm ? [{ label: 'ERPM', value: `${data.erpm}` }] : []),
+        ...(Number.isNaN(data.erpm) ? [] : [{ label: 'ERPM', value: `${data.erpm}` }]),
         { label: 'Distance', value: `${data.distance} ${units === 'metric' ? 'km' : 'mi'}` },
         '-',
         { label: 'State', value: data.state.toUpperCase(), color: getStateColor(data.state) },
@@ -81,9 +81,15 @@
       items={[
         { label: 'Duty', value: `${data.duty}%`, color: data.duty > 80 ? 'red' : ChartColours.DutyCycle },
         { label: 'Motor Current', value: `${data.current_motor} A`, color: ChartColours.CurrentMotor },
-        ...(data.current_field_weakening
-          ? [{ label: 'Field Weakening', value: `${data.current_field_weakening} A`, color: ChartColours.CurrentMotor }]
-          : []),
+        ...(Number.isNaN(data.current_field_weakening)
+          ? []
+          : [
+              {
+                label: 'Field Weakening',
+                value: `${data.current_field_weakening} A`,
+                color: ChartColours.CurrentMotor,
+              },
+            ]),
         '-',
         { label: 'Temp Motor', value: `${data.temp_motor}°C`, color: ChartColours.TempMotor },
         { label: 'Temp Controller', value: `${data.temp_mosfet}°C`, color: ChartColours.TempMosfet },
diff --git a/src/lib/parse/floaty.test.ts b/src/lib/parse/floaty.test.ts
index 8d7d132..c966562 100644
--- a/src/lib/parse/floaty.test.ts
+++ b/src/lib/parse/floaty.test.ts
@@ -8,11 +8,11 @@ describe(parseFloatyJson.name, () => {
     expect(units).toEqual('metric');
     expect(data).toHaveLength(3);
 
-    expect(data[0].gps_latitude).toBe(-1.0);
-    expect(data[0].gps_longitude).toBe(1.5);
-    expect(data[1].gps_latitude).toBe(-1.1);
-    expect(data[1].gps_longitude).toBe(1.6);
-    expect(data[2].gps_latitude).toBe(-1.1);
-    expect(data[2].gps_longitude).toBe(1.6);
+    expect(data[0]!.gps_latitude).toBe(-1.0);
+    expect(data[0]!.gps_longitude).toBe(1.5);
+    expect(data[1]!.gps_latitude).toBe(-1.1);
+    expect(data[1]!.gps_longitude).toBe(1.6);
+    expect(data[2]!.gps_latitude).toBe(-1.1);
+    expect(data[2]!.gps_longitude).toBe(1.6);
   });
 });
diff --git a/src/lib/parse/floaty.ts b/src/lib/parse/floaty.ts
index ea7d6dd..cd89ca8 100644
--- a/src/lib/parse/floaty.ts
+++ b/src/lib/parse/floaty.ts
@@ -5,7 +5,7 @@ import { stateCodeMap, type Row } from './types';
 
 function rowsFromFloatyJson(json: ZFloatyJson): Row[] {
   const rows: Row[] = [];
-  const map = (log: ZLog, location: ZLocation) => ({
+  const map = (log: ZLog, location: ZLocation): Row => ({
     adc1: log.adc1,
     adc2: log.adc2,
     ah_charged: NaN,
@@ -36,7 +36,7 @@ function rowsFromFloatyJson(json: ZFloatyJson): Row[] {
     setpoint: NaN,
     speed: log.speed,
     state_raw: log.state,
-    state: stateCodeMap[log.state],
+    state: stateCodeMap[log.state] ?? '??',
     temp_battery: NaN,
     temp_mosfet: log.controllerTemp,
     temp_motor: log.motorTemp,
@@ -50,10 +50,10 @@ function rowsFromFloatyJson(json: ZFloatyJson): Row[] {
   const { logs, locations } = json;
   let locationIdx = 0;
   for (let i = 0; i < logs.length; ++i) {
-    const log = logs[i];
-    let location = locations[locationIdx];
+    const log = logs[i]!;
+    let location = locations[locationIdx]!;
     if (location.timestamp < log.timestamp && locations[locationIdx + 1]) {
-      location = locations[++locationIdx];
+      location = locations[++locationIdx]!;
     }
 
     rows.push(map(log, location));
diff --git a/tsconfig.json b/tsconfig.json
index 26443a3..e70d115 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -16,8 +16,7 @@
     "isolatedModules": true,
     "strict": true,
     "noUnusedLocals": true,
-    // TODO: enable
-    "noUncheckedIndexedAccess": false,
+    "noUncheckedIndexedAccess": true,
     "moduleDetection": "force"
   },
   "include": ["src/**/*.ts", "src/**/*.js", "src/**/*.svelte"],