diff --git a/package.json5 b/package.json5
index 42f4b76..6c809b4 100644
--- a/package.json5
+++ b/package.json5
@@ -18,5 +18,6 @@
   license: 'Apache-2.0',
   dependencies: {
     'over.ts': 'github:m93a/over.ts',
+    typescript: '^4.8.2',
   },
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 01f6172..f729120 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2,12 +2,20 @@ lockfileVersion: 5.4
 
 specifiers:
   over.ts: github:m93a/over.ts
+  typescript: ^4.8.2
 
 dependencies:
   over.ts: github.com/m93a/over.ts/0fd6e18afd4ca5a23c9e09d1fcd6b7357b642247
+  typescript: 4.8.2
 
 packages:
 
+  /typescript/4.8.2:
+    resolution: {integrity: sha512-C0I1UsrrDHo2fYI5oaCGbSejwX4ch+9Y5jTQELvovfmFkK3HHSZJB8MSJcWLmCUBzQBchCrZ9rMRV6GuNrvGtw==}
+    engines: {node: '>=4.2.0'}
+    hasBin: true
+    dev: false
+
   github.com/m93a/over.ts/0fd6e18afd4ca5a23c9e09d1fcd6b7357b642247:
     resolution: {tarball: https://codeload.github.com/m93a/over.ts/tar.gz/0fd6e18afd4ca5a23c9e09d1fcd6b7357b642247}
     name: over.ts
diff --git a/src/steps/one.ts b/src/steps/one.ts
index 7300e34..b9b3f86 100644
--- a/src/steps/one.ts
+++ b/src/steps/one.ts
@@ -1,4 +1,4 @@
-import { useTypes } from 'over';
+import { useTypes } from 'over.ts/src/index';
 
 const types = {
    number: (x: unknown): x is number => typeof x === 'number',
@@ -7,12 +7,26 @@ const types = {
 
 const overload = useTypes(types)
 
+const negate = overload({
+   'number -> number': (a: number): number => {
+      console.log('Negating number', a)
+      return -a
+   },
+   'bigint -> bigint': (a: bigint): bigint => {
+      console.log('Negating bigint', a)
+      return -a
+   }
+})
+
+console.log('Negation of 5 is', negate(5))
+console.log('Negation of 5n is', negate(5n))
+
 const add = overload({
-   'number,number -> number': (a,b) => {
+   'number, number -> number': (a: number, b: number): number => {
       console.log('Adding numbers', a, b)
       return a+b
    },
-   'bigint,bigint -> bigint': (a,b) => {
+   'bigint, bigint -> bigint': (a: bigint, b: bigint): bigint => {
       console.log('Adding bigints', a, b)
       return a+b
    }
@@ -20,3 +34,10 @@ const add = overload({
 
 console.log('Sum of 5 and 7 is', add(5,7))
 console.log('Sum of 5n and 7n is', add(5n, 7n))
+
+try {
+    //@ts-expect-error
+    console.log('Mixed sum is', add(5n, 7))
+} catch {
+    console.log('Mixed sum errored as expected.')
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..d17d548
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,9 @@
+{
+    "compilerOptions": {
+        "target": "ES2022",
+        "moduleResolution": "node"
+    },
+    "files": [
+        "src/steps/one.ts"
+    ]
+}