diff --git a/src/index.test.ts b/src/index.test.ts
index 24b6a2e..3f47feb 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -1,7 +1,7 @@
 import { test } from "node:test";
 import { strict as assert } from "node:assert";
 import { expectTypeOf } from "expect-type";
-import { match, P, type Matcher } from "./index.js";
+import { match, P, type Matcher } from "./index.ts";
 
 test("match returns a builder", () => {
     const builder = match("x");
diff --git a/src/index.ts b/src/index.ts
index 970ea6a..20f0ec7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,2 +1,2 @@
-export { match, P } from "./match.js";
-export type { Matcher, Pattern } from "./pattern.js";
+export { match, P } from "./match.ts";
+export type { Matcher, Pattern } from "./pattern.ts";
diff --git a/src/match.ts b/src/match.ts
index 6487acb..a7b6c84 100644
--- a/src/match.ts
+++ b/src/match.ts
@@ -1,4 +1,4 @@
-import { P, type Matcher, type Pattern } from "./pattern.js";
+import { P, type Matcher, type Pattern } from "./pattern.ts";
 
 type Cases<R> = ReadonlyArray<
     readonly [Matcher<unknown>, (value: unknown) => R]
diff --git a/tsconfig.build.json b/tsconfig.build.json
index dd7d10f..2342359 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -2,6 +2,7 @@
     "extends": "./tsconfig.json",
     "compilerOptions": {
         "noEmit": false,
+        "rewriteRelativeImportExtensions": true,
         "rootDir": "src",
         "outDir": "dist"
     },
diff --git a/tsconfig.json b/tsconfig.json
index e5c3c91..e3bea47 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -23,6 +23,7 @@
         "noUnusedParameters": true,
         "isolatedModules": true,
         "verbatimModuleSyntax": true,
+        "allowImportingTsExtensions": true,
         "declaration": true,
         "declarationMap": true,
         "sourceMap": true,
@@ -34,4 +35,4 @@
         "types": ["node"]
     },
     "include": ["src"]
-}
\ No newline at end of file
+}