diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 456231e..554191c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -26,6 +26,9 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
+      - name: Typecheck
+        run: pnpm typecheck
+
       - name: Test
         run: pnpm test -- --coverage
 
diff --git a/package.json b/package.json
index 781ef88..8159273 100644
--- a/package.json
+++ b/package.json
@@ -37,7 +37,8 @@
     "prepack": "pnpm build",
     "release": "np",
     "start": "pnpm build -- --watch",
-    "test": "vitest run"
+    "test": "vitest run",
+    "typecheck": "tsc --noEmit"
   },
   "dependencies": {
     "chalk": "^5.3.0",
diff --git a/src/index.ts b/src/index.ts
index cb8a183..cce0ef7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -4,6 +4,7 @@ import * as fs from 'fs/promises';
 import { Plugin } from 'vite';
 import { execaCommand } from 'execa';
 import { npmRunPathEnv } from 'npm-run-path';
+import * as stream from 'stream';
 import chalk from 'chalk';
 import parseCompilerLog from './parseCompilerLog.js';
 
@@ -31,7 +32,7 @@ async function launchReScript(
 
   let compileOnce = (_value: unknown) => {};
 
-  function dataListener(chunk: any) {
+  function dataListener(chunk: stream.Readable) {
     const output = chunk.toString().trimEnd();
     if (!silent) {
       // eslint-disable-next-line no-console
@@ -134,7 +135,7 @@ export default function createReScriptPlugin(config?: Config): Plugin {
       );
     },
     // Hook that resolves `.bs.js` imports to their `.res` counterpart
-    async resolveId(source, importer, options: any) {
+    async resolveId(source, importer, options) {
       if (source.endsWith('.res')) usingLoader = true;
       if (options.isEntry || !importer) return null;
       if (!importer.endsWith('.res')) return null;
diff --git a/src/parseCompilerLog.ts b/src/parseCompilerLog.ts
index 3c0c6ee..5b7b8cb 100644
--- a/src/parseCompilerLog.ts
+++ b/src/parseCompilerLog.ts
@@ -13,10 +13,10 @@ const codeRegex = /^  +([0-9]+| +|\.) (│|┆)/;
 const warningErrorRegex = /Warning number \d+ \(configured as error\)/;
 
 // Returns true if the line indicates the start of an error block
-function isErrorLine(line: string) {
-  if (line.startsWith("  We've found a bug for you!")) return true;
-  if (line.startsWith('  Syntax error!')) return true;
-  if (warningErrorRegex.test(line)) return true;
+function isErrorLine(line: string | undefined) {
+  if (line?.startsWith("  We've found a bug for you!")) return true;
+  if (line?.startsWith('  Syntax error!')) return true;
+  if (line && warningErrorRegex.test(line)) return true;
   return false;
 }
 
@@ -34,7 +34,7 @@ export default function parseCompilerLog(
   // Optimization; only parse log when compiler is done
   if (lines[lines.length - 1]?.startsWith('#Done(')) {
     let foundError = false;
-    let path = '';
+    let path: string | undefined;
     let startLine = 0;
 
     // There can be additional messages such as hints
@@ -58,39 +58,41 @@ export default function parseCompilerLog(
 
         // Optimization; the next line is always the file + range, which means it
         // can be parsed now and the next iteration (line) can be skipped.
-        path = lines[i + 1].trim();
+        path = lines?.[i + 1]?.trim();
 
         // Extract the start line
-        const match = path.match(fileAndRangeRegex);
-        if (match) startLine = parseInt(match[2], 10);
+        const match = path?.match(fileAndRangeRegex);
+        if (match) startLine = Number(match[2]);
 
         // Skip the next line since it was handled here
         i += 1;
       } else if (!foundError) {
         // Only run below checks once an error has been found
-      } else if (line.startsWith('  Warning number ')) {
+      } else if (line?.startsWith('  Warning number ')) {
         // Reached the end of the error
         break;
-      } else if (line.startsWith('#Done(')) {
+      } else if (line?.startsWith('#Done(')) {
         // Reached the end of the log file
         break;
       } else {
         // This can now only be code lines or messages
-        const match = line.match(codeRegex);
+        const match = line?.match(codeRegex);
         if (match) {
           // Replace strange vertical bars with regular ones in order to match
           // the code frame regex defined in the vite overlay file:
           // https://github.com/vitejs/vite/blob/96591bf9989529de839ba89958755eafe4c445ae/packages/vite/src/client/overlay.ts#L116
-          let codeFrameLine = line.replace('┆', '|').replace('│', '|');
+          let codeFrameLine = line?.replace('┆', '|').replace('│', '|');
 
           // Since the red color indicator is lost when parsing the log file,
           // this adds a pointer (`>`) to the line where the error starts.
-          if (parseInt(match[1], 10) === startLine) {
-            codeFrameLine = `> ${codeFrameLine.substring(2)}`;
+          if (Number(match[1]) === startLine) {
+            codeFrameLine = `> ${codeFrameLine?.substring(2)}`;
           }
 
-          frame.push(codeFrameLine);
-        } else if (line.startsWith('  ')) {
+          if (codeFrameLine) {
+            frame.push(codeFrameLine);
+          }
+        } else if (line?.startsWith('  ')) {
           // It has to be a message by now
           messages.push(line.trim());
         }
diff --git a/test/index.test.ts b/test/index.test.ts
index 78bb055..60474f6 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -12,6 +12,9 @@ describe('@jihchi/vite-plugin-rescript', () => {
   it('invokes closeBundle hook without crashing', async () => {
     const actual = Plugin();
     expect(actual).toHaveProperty('closeBundle');
-    await expect(actual.closeBundle()).resolves.toEqual(undefined);
+    await expect(
+      // @ts-expect-error
+      actual.closeBundle()
+    ).resolves.toEqual(undefined);
   });
 });