diff --git a/.gitignore b/.gitignore
index a547bf3..0256e41 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,6 +12,12 @@ dist
 dist-ssr
 *.local
 
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional eslint cache
+.eslintcache
+
 # Editor directories and files
 .vscode/*
 !.vscode/extensions.json
diff --git a/src/App.tsx b/src/App.tsx
index 093c0f7..1001fb4 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -35,7 +35,7 @@ function App() {
 
   // Create scales
   const xScale = d3
-    .scaleBand()
+    .scaleBand<number>()
     .domain(sortedResponses)
     .range([0, sortedResponses.length * config.groupSpacing]);
   return (
diff --git a/src/components/QuestionGroupChart.tsx b/src/components/QuestionGroupChart.tsx
index 057c5ec..a8b4dd2 100644
--- a/src/components/QuestionGroupChart.tsx
+++ b/src/components/QuestionGroupChart.tsx
@@ -10,9 +10,9 @@ import "./Chart.css";
 interface QuestionGroupChartProps {
   question: string;
   metadata?: CategoryMetadata;
-  groupData: { response: string }[];
-  responses: string[];
-  xScale: d3.ScaleBand<string>;
+  groupData: { response: number }[];
+  responses: number[];
+  xScale: d3.ScaleBand<number>;
 }
 
 function makeDot(