diff --git a/src/preflight.cts b/src/preflight.cts
index 1e872f72..ed03c27b 100644
--- a/src/preflight.cts
+++ b/src/preflight.cts
@@ -1,6 +1,18 @@
 import { constants as osConstants } from 'os';
 import './suppress-warnings.cts';
 
+/**
+ * Hook require() to transform to CJS
+ *
+ * This needs to be loaded via --require flag so subsequent --require
+ * flags can support TypeScript.
+ *
+ * This is also added in loader.ts for the loader API.
+ * Although it is required twice, it's not executed twice because
+ * it's cached.
+ */
+require('@esbuild-kit/cjs-loader');
+
 // If a parent process is detected
 if (process.send) {
 	function relaySignal(signal: NodeJS.Signals) {
diff --git a/tests/fixtures/log-argv.ts b/tests/fixtures/log-argv.ts
index 4f94da66..a8fd079c 100644
--- a/tests/fixtures/log-argv.ts
+++ b/tests/fixtures/log-argv.ts
@@ -1 +1 @@
-console.log(JSON.stringify(process.argv));
+console.log(JSON.stringify(process.argv) as string); // Unnecessary TS syntax to test
diff --git a/tests/specs/typescript/ts.ts b/tests/specs/typescript/ts.ts
index 09f174e1..d9cbd37a 100644
--- a/tests/specs/typescript/ts.ts
+++ b/tests/specs/typescript/ts.ts
@@ -50,6 +50,11 @@ export default testSuite(async ({ describe }, node: NodeApis) => {
 				assertResults(nodeProcess, true);
 				expect(nodeProcess.stdout).toMatch('{"default":1234}');
 			});
+
+			test('Require flag', async () => {
+				const nodeProcess = await node.requireFlag(importPath);
+				assertResults(nodeProcess, true);
+			});
 		});
 
 		describe('full path via .js', ({ test }) => {
diff --git a/tests/utils/tsx.ts b/tests/utils/tsx.ts
index dc393951..ef586fc4 100644
--- a/tests/utils/tsx.ts
+++ b/tests/utils/tsx.ts
@@ -93,6 +93,19 @@ export async function createNode(
 				cwd: fixturePath,
 			});
 		},
+		requireFlag(
+			filePath: string,
+		) {
+			return this.tsx({
+				args: [
+					'--eval',
+					'null',
+					'--require',
+					filePath,
+				],
+				cwd: fixturePath,
+			});
+		},
 	};
 }