diff --git a/packages/format-csv/__typetests__/index.test-d.ts b/packages/format-csv/__typetests__/index.test-d.ts
new file mode 100644
index 000000000..f61407344
--- /dev/null
+++ b/packages/format-csv/__typetests__/index.test-d.ts
@@ -0,0 +1,5 @@
+import { CatalogFormatter } from "@lingui/conf"
+import { expectAssignable } from "tsd"
+import { formatter } from "@lingui/format-csv"
+
+expectAssignable<CatalogFormatter>(formatter())
diff --git a/packages/format-csv/__typetests__/tsconfig.json b/packages/format-csv/__typetests__/tsconfig.json
new file mode 100644
index 000000000..114e1ccd5
--- /dev/null
+++ b/packages/format-csv/__typetests__/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "moduleResolution": "Node16",
+    "skipLibCheck": true,
+    "esModuleInterop": true
+  },
+  "paths": {}
+}
diff --git a/packages/format-csv/package.json b/packages/format-csv/package.json
index e3f5bf9b4..bec7c2b7c 100644
--- a/packages/format-csv/package.json
+++ b/packages/format-csv/package.json
@@ -41,6 +41,7 @@
     "papaparse": "^5.4.0"
   },
   "devDependencies": {
+    "tsd": "^0.28.0",
     "unbuild": "^1.1.2"
   }
 }
diff --git a/packages/format-json/__typetests__/index.test-d.ts b/packages/format-json/__typetests__/index.test-d.ts
new file mode 100644
index 000000000..420544cb0
--- /dev/null
+++ b/packages/format-json/__typetests__/index.test-d.ts
@@ -0,0 +1,8 @@
+import { CatalogFormatter } from "@lingui/conf"
+import { expectAssignable } from "tsd"
+import { formatter } from "@lingui/format-json"
+
+expectAssignable<CatalogFormatter>(formatter())
+expectAssignable<CatalogFormatter>(
+  formatter({ lineNumbers: true, origins: true })
+)
diff --git a/packages/format-json/__typetests__/tsconfig.json b/packages/format-json/__typetests__/tsconfig.json
new file mode 100644
index 000000000..114e1ccd5
--- /dev/null
+++ b/packages/format-json/__typetests__/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "moduleResolution": "Node16",
+    "skipLibCheck": true,
+    "esModuleInterop": true
+  },
+  "paths": {}
+}
diff --git a/packages/format-json/package.json b/packages/format-json/package.json
index d1297a487..a0d98d6bf 100644
--- a/packages/format-json/package.json
+++ b/packages/format-json/package.json
@@ -41,6 +41,7 @@
     "ramda": "^0.28.0"
   },
   "devDependencies": {
+    "tsd": "^0.28.0",
     "unbuild": "^1.1.2"
   }
 }
diff --git a/packages/format-po-gettext/__typetests__/index.test-d.ts b/packages/format-po-gettext/__typetests__/index.test-d.ts
new file mode 100644
index 000000000..cafbd2834
--- /dev/null
+++ b/packages/format-po-gettext/__typetests__/index.test-d.ts
@@ -0,0 +1,13 @@
+import { CatalogFormatter } from "@lingui/conf"
+import { expectAssignable } from "tsd"
+import { formatter } from "@lingui/format-po-gettext"
+
+expectAssignable<CatalogFormatter>(formatter())
+expectAssignable<CatalogFormatter>(
+  formatter({
+    lineNumbers: true,
+    origins: true,
+    printLinguiId: true,
+    disableSelectWarning: true,
+  })
+)
diff --git a/packages/format-po-gettext/__typetests__/tsconfig.json b/packages/format-po-gettext/__typetests__/tsconfig.json
new file mode 100644
index 000000000..114e1ccd5
--- /dev/null
+++ b/packages/format-po-gettext/__typetests__/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "moduleResolution": "Node16",
+    "skipLibCheck": true,
+    "esModuleInterop": true
+  },
+  "paths": {}
+}
diff --git a/packages/format-po-gettext/package.json b/packages/format-po-gettext/package.json
index 5faf27d84..6abf61ae7 100644
--- a/packages/format-po-gettext/package.json
+++ b/packages/format-po-gettext/package.json
@@ -49,6 +49,7 @@
   },
   "devDependencies": {
     "@lingui/jest-mocks": "workspace:^",
+    "tsd": "^0.28.0",
     "unbuild": "^1.1.2"
   }
 }
diff --git a/packages/format-po-gettext/src/po-gettext.test.ts b/packages/format-po-gettext/src/po-gettext.test.ts
index 48f93b8a5..96ddaacaf 100644
--- a/packages/format-po-gettext/src/po-gettext.test.ts
+++ b/packages/format-po-gettext/src/po-gettext.test.ts
@@ -2,11 +2,24 @@ import { mockConsole } from "@lingui/jest-mocks"
 import fs from "fs"
 import path from "path"
 
-import { CatalogType } from "@lingui/conf"
+import { CatalogFormatter, CatalogType } from "@lingui/conf"
 import { formatter as createFormat } from "./po-gettext"
 
+const defaultParseCtx: Parameters<CatalogFormatter["parse"]>[1] = {
+  locale: "en",
+  sourceLocale: "en",
+  filename: "file.po",
+}
+
+const defaultSerializeCtx: Parameters<CatalogFormatter["serialize"]>[1] = {
+  locale: "en",
+  existing: null,
+  filename: "file.po",
+  sourceLocale: "en",
+}
+
 describe("po-gettext format", () => {
-  let format = createFormat()
+  const format = createFormat()
 
   afterEach(() => {
     jest.useRealTimers()
@@ -50,10 +63,7 @@ describe("po-gettext format", () => {
       },
     }
 
-    const pofile = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const pofile = format.serialize(catalog, defaultSerializeCtx)
 
     expect(pofile).toMatchSnapshot()
   })
@@ -63,7 +73,8 @@ describe("po-gettext format", () => {
       .readFileSync(path.join(__dirname, "fixtures/messages_plural.po"))
       .toString()
 
-    const catalog = format.parse(pofile)
+    const catalog = format.parse(pofile, defaultParseCtx)
+
     expect(catalog).toMatchSnapshot()
   })
 
@@ -94,7 +105,7 @@ describe("po-gettext format", () => {
     }
 
     mockConsole((console) => {
-      format.serialize(catalog, { existing: null, locale: "en" })
+      format.serialize(catalog, defaultSerializeCtx)
 
       expect(console.warn).toHaveBeenCalledWith(
         expect.stringContaining("Nested plurals"),
@@ -118,7 +129,7 @@ msgstr[1] "# dny"
 msgstr[2] "# dní"
   `
 
-    const parsed = format.parse(po)
+    const parsed = format.parse(po, defaultParseCtx)
 
     expect(parsed).toEqual({
       Y8Xw2Y: {
@@ -145,7 +156,7 @@ msgstr[2] "# dní"
 
     it("should warn", () => {
       mockConsole((console) => {
-        format.serialize(catalog, { locale: "en", existing: null })
+        format.serialize(catalog, defaultSerializeCtx)
 
         expect(console.warn).toHaveBeenCalledWith(
           expect.stringContaining("select"),
@@ -158,7 +169,7 @@ msgstr[2] "# dní"
       const format = createFormat({ disableSelectWarning: true })
 
       mockConsole((console) => {
-        format.serialize(catalog, { locale: "en", existing: null })
+        format.serialize(catalog, defaultSerializeCtx)
 
         expect(console.warn).not.toHaveBeenCalled()
       })
@@ -175,7 +186,7 @@ msgstr[2] "# dní"
 
     it("should warn", () => {
       mockConsole((console) => {
-        format.serialize(catalog, { locale: "en", existing: null })
+        format.serialize(catalog, defaultSerializeCtx)
 
         expect(console.warn).toHaveBeenCalledWith(
           expect.stringContaining("selectOrdinal"),
@@ -188,7 +199,7 @@ msgstr[2] "# dní"
       const format = createFormat({ disableSelectWarning: true })
 
       mockConsole((console) => {
-        format.serialize(catalog, { locale: "en", existing: null })
+        format.serialize(catalog, defaultSerializeCtx)
 
         expect(console.warn).not.toHaveBeenCalled()
       })
@@ -202,7 +213,8 @@ msgstr[2] "# dní"
       )
       .toString()
 
-    const catalog = format.parse(pofile)
+    const catalog = format.parse(pofile, defaultParseCtx)
+
     expect(catalog).toMatchSnapshot()
   })
 })
diff --git a/packages/format-po-gettext/src/po-gettext.ts b/packages/format-po-gettext/src/po-gettext.ts
index f59d317ad..aab6e55a8 100644
--- a/packages/format-po-gettext/src/po-gettext.ts
+++ b/packages/format-po-gettext/src/po-gettext.ts
@@ -238,7 +238,9 @@ const convertPluralsToICU = (
   item.msgstr = ["{" + pluralizeOn + ", plural, " + pluralClauses + "}"]
 }
 
-export function formatter(options: PoGettextFormatterOptions = {}) {
+export function formatter(
+  options: PoGettextFormatterOptions = {}
+): CatalogFormatter {
   options = {
     origins: true,
     lineNumbers: true,
@@ -251,7 +253,7 @@ export function formatter(options: PoGettextFormatterOptions = {}) {
     catalogExtension: ".po",
     templateExtension: ".pot",
 
-    parse(content): CatalogType {
+    parse(content, ctx): CatalogType {
       const po = PO.parse(content)
 
       // .po plurals are numbered 0-N and need to be mapped to ICU plural classes ("one", "few", "many"...). Different
@@ -263,14 +265,11 @@ export function formatter(options: PoGettextFormatterOptions = {}) {
         convertPluralsToICU(item, pluralForms, po.headers.Language)
       })
 
-      return formatter.parse(po.toString())
+      return formatter.parse(po.toString(), ctx) as CatalogType
     },
 
-    serialize(
-      catalog: CatalogType,
-      ctx: { locale: string; existing: string }
-    ): string {
-      const po = PO.parse(formatter.serialize(catalog, ctx))
+    serialize(catalog, ctx): string {
+      const po = PO.parse(formatter.serialize(catalog, ctx) as string)
 
       po.items = po.items.map((item) => {
         const isGeneratedId = !item.flags["explicit-id"]
@@ -283,5 +282,5 @@ export function formatter(options: PoGettextFormatterOptions = {}) {
 
       return po.toString()
     },
-  } satisfies CatalogFormatter
+  }
 }
diff --git a/packages/format-po/__typetests__/index.test-d.ts b/packages/format-po/__typetests__/index.test-d.ts
new file mode 100644
index 000000000..2b850dcb1
--- /dev/null
+++ b/packages/format-po/__typetests__/index.test-d.ts
@@ -0,0 +1,12 @@
+import { CatalogFormatter } from "@lingui/conf"
+import { expectAssignable } from "tsd"
+import { formatter } from "@lingui/format-po"
+
+expectAssignable<CatalogFormatter>(formatter())
+expectAssignable<CatalogFormatter>(
+  formatter({
+    lineNumbers: true,
+    origins: true,
+    printLinguiId: true,
+  })
+)
diff --git a/packages/format-po/__typetests__/tsconfig.json b/packages/format-po/__typetests__/tsconfig.json
new file mode 100644
index 000000000..114e1ccd5
--- /dev/null
+++ b/packages/format-po/__typetests__/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "moduleResolution": "Node16",
+    "skipLibCheck": true,
+    "esModuleInterop": true
+  },
+  "paths": {}
+}
diff --git a/packages/format-po/package.json b/packages/format-po/package.json
index 8f3efec39..0f66ba40d 100644
--- a/packages/format-po/package.json
+++ b/packages/format-po/package.json
@@ -46,6 +46,7 @@
   },
   "devDependencies": {
     "@lingui/jest-mocks": "workspace:^",
+    "tsd": "^0.28.0",
     "unbuild": "^1.1.2"
   }
 }
diff --git a/packages/format-po/src/po.test.ts b/packages/format-po/src/po.test.ts
index efbb459a7..3b6d15735 100644
--- a/packages/format-po/src/po.test.ts
+++ b/packages/format-po/src/po.test.ts
@@ -2,7 +2,20 @@ import fs from "fs"
 import path from "path"
 
 import { formatter as createFormatter } from "./po"
-import { CatalogType } from "@lingui/conf"
+import { CatalogFormatter, CatalogType } from "@lingui/conf"
+
+const defaultParseCtx: Parameters<CatalogFormatter["parse"]>[1] = {
+  locale: "en",
+  sourceLocale: "en",
+  filename: "file.po",
+}
+
+const defaultSerializeCtx: Parameters<CatalogFormatter["serialize"]>[1] = {
+  locale: "en",
+  existing: null,
+  filename: "file.po",
+  sourceLocale: "en",
+}
 
 describe("pofile format", () => {
   jest.useFakeTimers().setSystemTime(new Date("2018-08-27T10:00Z").getTime())
@@ -65,10 +78,7 @@ describe("pofile format", () => {
       },
     }
 
-    const pofile = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const pofile = format.serialize(catalog, defaultSerializeCtx)
     expect(pofile).toMatchSnapshot()
   })
 
@@ -79,7 +89,7 @@ describe("pofile format", () => {
       .readFileSync(path.join(__dirname, "fixtures/messages.po"))
       .toString()
 
-    const actual = format.parse(pofile)
+    const actual = format.parse(pofile, defaultParseCtx)
     expect(actual).toMatchSnapshot()
   })
 
@@ -95,12 +105,9 @@ describe("pofile format", () => {
       },
     }
 
-    const serialized = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const serialized = format.serialize(catalog, defaultSerializeCtx) as string
 
-    const actual = format.parse(serialized)
+    const actual = format.parse(serialized, defaultParseCtx)
     expect(actual).toMatchObject(catalog)
   })
 
@@ -116,10 +123,7 @@ describe("pofile format", () => {
       },
     }
 
-    const serialized = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const serialized = format.serialize(catalog, defaultSerializeCtx)
 
     expect(serialized).toMatchSnapshot()
   })
@@ -137,10 +141,7 @@ describe("pofile format", () => {
       },
     }
 
-    const serialized = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const serialized = format.serialize(catalog, defaultSerializeCtx)
 
     expect(serialized).toMatchSnapshot()
   })
@@ -164,7 +165,7 @@ describe("pofile format", () => {
       msgstr "Second description joins translator comments"
     `
 
-    const actual = format.parse(po)
+    const actual = format.parse(po, defaultParseCtx)
     expect(actual).toMatchSnapshot()
   })
 
@@ -188,7 +189,7 @@ describe("pofile format", () => {
       },
     }
 
-    const actual = format.serialize(catalog, { locale: "en", existing: null })
+    const actual = format.serialize(catalog, defaultSerializeCtx)
     const pofileOriginPrefix = "#:"
     expect(actual).toEqual(expect.not.stringContaining(pofileOriginPrefix))
   })
@@ -212,10 +213,7 @@ describe("pofile format", () => {
         ],
       },
     }
-    const actual = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const actual = format.serialize(catalog, defaultSerializeCtx)
 
     expect(actual).toMatchInlineSnapshot(`
       msgid ""
@@ -262,10 +260,7 @@ describe("pofile format", () => {
       },
     }
 
-    const actual = format.serialize(catalog, {
-      locale: "en",
-      existing: null,
-    })
+    const actual = format.serialize(catalog, defaultSerializeCtx)
 
     expect(actual).toMatchInlineSnapshot(`
       msgid ""
diff --git a/packages/format-po/src/po.ts b/packages/format-po/src/po.ts
index b38ab379d..4c7641229 100644
--- a/packages/format-po/src/po.ts
+++ b/packages/format-po/src/po.ts
@@ -131,7 +131,7 @@ function deserialize(items: POItem[]): CatalogType {
   }, {})
 }
 
-export function formatter(options: PoFormatterOptions = {}) {
+export function formatter(options: PoFormatterOptions = {}): CatalogFormatter {
   options = {
     origins: true,
     lineNumbers: true,
@@ -142,15 +142,12 @@ export function formatter(options: PoFormatterOptions = {}) {
     catalogExtension: ".po",
     templateExtension: ".pot",
 
-    parse(content: string): CatalogType {
+    parse(content): CatalogType {
       const po = PO.parse(content)
       return deserialize(po.items)
     },
 
-    serialize(
-      catalog: CatalogType,
-      ctx: { locale: string; existing: string }
-    ): string {
+    serialize(catalog, ctx): string {
       let po: PO
 
       if (ctx.existing) {
@@ -165,5 +162,5 @@ export function formatter(options: PoFormatterOptions = {}) {
       po.items = serialize(catalog, options)
       return po.toString()
     },
-  } satisfies CatalogFormatter
+  }
 }
diff --git a/yarn.lock b/yarn.lock
index c9bce7c07..f777b02c5 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2721,6 +2721,7 @@ __metadata:
   dependencies:
     "@lingui/conf": 4.0.0-next.3
     papaparse: ^5.4.0
+    tsd: ^0.28.0
     unbuild: ^1.1.2
   languageName: unknown
   linkType: soft
@@ -2731,6 +2732,7 @@ __metadata:
   dependencies:
     "@lingui/conf": 4.0.0-next.3
     ramda: ^0.28.0
+    tsd: ^0.28.0
     unbuild: ^1.1.2
   languageName: unknown
   linkType: soft
@@ -2747,6 +2749,7 @@ __metadata:
     node-gettext: ^3.0.0
     plurals-cldr: ^2.0.1
     pofile: ^1.1.4
+    tsd: ^0.28.0
     unbuild: ^1.1.2
   languageName: unknown
   linkType: soft
@@ -2760,6 +2763,7 @@ __metadata:
     "@lingui/jest-mocks": "workspace:^"
     date-fns: ^2.29.3
     pofile: ^1.1.4
+    tsd: ^0.28.0
     unbuild: ^1.1.2
   languageName: unknown
   linkType: soft
@@ -3724,6 +3728,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@tsd/typescript@npm:~5.0.2":
+  version: 5.0.2
+  resolution: "@tsd/typescript@npm:5.0.2"
+  checksum: ab9274c5208ec882840d3cbddd897fb14699afe2a71a6039027f60a4d1f5b37746f41a0dbc385ebef363717c5490e45f15308c0cfb023393194afaca24d66850
+  languageName: node
+  linkType: hard
+
 "@types/aria-query@npm:^4.2.0":
   version: 4.2.2
   resolution: "@types/aria-query@npm:4.2.2"
@@ -9143,6 +9154,18 @@ __metadata:
   languageName: node
   linkType: hard
 
+"jest-diff@npm:^29.0.3":
+  version: 29.5.0
+  resolution: "jest-diff@npm:29.5.0"
+  dependencies:
+    chalk: ^4.0.0
+    diff-sequences: ^29.4.3
+    jest-get-type: ^29.4.3
+    pretty-format: ^29.5.0
+  checksum: dfd0f4a299b5d127779c76b40106c37854c89c3e0785098c717d52822d6620d227f6234c3a9291df204d619e799e3654159213bf93220f79c8e92a55475a3d39
+  languageName: node
+  linkType: hard
+
 "jest-diff@npm:^29.4.3":
   version: 29.4.3
   resolution: "jest-diff@npm:29.4.3"
@@ -12061,6 +12084,17 @@ __metadata:
   languageName: node
   linkType: hard
 
+"pretty-format@npm:^29.5.0":
+  version: 29.5.0
+  resolution: "pretty-format@npm:29.5.0"
+  dependencies:
+    "@jest/schemas": ^29.4.3
+    ansi-styles: ^5.0.0
+    react-is: ^18.0.0
+  checksum: 4065356b558e6db25b4d41a01efb386935a6c06a0c9c104ef5ce59f2f476b8210edb8b3949b386e60ada0a6dc5ebcb2e6ccddc8c64dfd1a9943c3c3a9e7eaf89
+  languageName: node
+  linkType: hard
+
 "proc-log@npm:^2.0.0, proc-log@npm:^2.0.1":
   version: 2.0.1
   resolution: "proc-log@npm:2.0.1"
@@ -13943,6 +13977,23 @@ __metadata:
   languageName: node
   linkType: hard
 
+"tsd@npm:^0.28.0":
+  version: 0.28.0
+  resolution: "tsd@npm:0.28.0"
+  dependencies:
+    "@tsd/typescript": ~5.0.2
+    eslint-formatter-pretty: ^4.1.0
+    globby: ^11.0.1
+    jest-diff: ^29.0.3
+    meow: ^9.0.0
+    path-exists: ^4.0.0
+    read-pkg-up: ^7.0.0
+  bin:
+    tsd: dist/cli.js
+  checksum: 9dd5d58a1e568127b7e2ad6e91b2b791e81c807dfe063fa7547a756a0c3d5ca1366b19097cc6aa6d048d6b20d704469e511da5caf5db6d2b4283019187ad3130
+  languageName: node
+  linkType: hard
+
 "tslib@npm:^1.8.1, tslib@npm:^1.9.0":
   version: 1.14.1
   resolution: "tslib@npm:1.14.1"