diff --git a/locale/_/pronouns/morphemes.ts b/locale/_/pronouns/morphemes.ts
new file mode 100644
index 000000000..8eb27f173
--- /dev/null
+++ b/locale/_/pronouns/morphemes.ts
@@ -0,0 +1 @@
+export default [] as const;
diff --git a/locale/_/pronouns/morphemes.js b/locale/_base/pronouns/morphemes.ts
similarity index 91%
rename from locale/_/pronouns/morphemes.js
rename to locale/_base/pronouns/morphemes.ts
index f082fdb28..0005ffc65 100644
--- a/locale/_/pronouns/morphemes.js
+++ b/locale/_base/pronouns/morphemes.ts
@@ -4,4 +4,4 @@ export default [
     'possessive_determiner',
     'possessive_pronoun',
     'reflexive',
-];
+] as const;
diff --git a/locale/ar/pronouns/morphemes.js b/locale/ar/pronouns/morphemes.ts
similarity index 94%
rename from locale/ar/pronouns/morphemes.js
rename to locale/ar/pronouns/morphemes.ts
index 45f918bad..38fd844ab 100644
--- a/locale/ar/pronouns/morphemes.js
+++ b/locale/ar/pronouns/morphemes.ts
@@ -11,4 +11,4 @@ export default [
     'future',
     'order',
     'noun_end',
-];
+] as const;
diff --git a/locale/data.ts b/locale/data.ts
new file mode 100644
index 000000000..189e8fbe7
--- /dev/null
+++ b/locale/data.ts
@@ -0,0 +1,28 @@
+export type PronounData<M extends string> = {
+    key: string;
+    description: string;
+    normative: boolean;
+    plural: boolean;
+    pluralHonorific: boolean;
+    pronounceable: boolean;
+    history?: string;
+    thirdForm?: M;
+    smallForm?: M;
+    sourcesInfo?: string;
+    hidden?: boolean;
+} & { [morpheme in M]: string | null };
+
+export interface PronounExamplesData {
+    singular: string;
+    plural?: string;
+    isHonorific?: boolean;
+}
+
+export interface NounTemplatesData {
+    masc: string;
+    fem: string;
+    neutr: string;
+    mascPl: string;
+    femPl: string;
+    neutrPl: string;
+}
diff --git a/locale/dataFiles.ts b/locale/dataFiles.ts
new file mode 100644
index 000000000..c758200df
--- /dev/null
+++ b/locale/dataFiles.ts
@@ -0,0 +1,34 @@
+declare module '*/config.suml' {
+    import type { Config } from '~/locale/config.ts';
+    const config: Config;
+    export default config;
+}
+
+declare module '*/translations.suml' {
+    import type { Translations } from '~/locale/translations.ts';
+    const translations: Translations;
+    export default translations;
+}
+
+declare module '*/pronouns/pronouns.tsv' {
+    import type { PronounData } from '~/locale/data.ts';
+    const data: PronounData<string>[];
+    export default data;
+}
+
+declare module '*/pronouns/examples.tsv' {
+    import type { PronounExamplesData } from '~/locale/data.ts';
+    const data: PronounExamplesData[];
+    export default data;
+}
+
+declare module '*/nouns/nounTemplates.tsv' {
+    import type { NounTemplatesData } from '~/locale/data.ts';
+    const data: NounTemplatesData[];
+    export default data;
+}
+
+declare module '*.tsv' {
+    const data: Record<string, any>[];
+    export default data;
+}
diff --git a/locale/de/pronouns/morphemes.js b/locale/de/pronouns/morphemes.js
deleted file mode 100644
index d5007aa68..000000000
--- a/locale/de/pronouns/morphemes.js
+++ /dev/null
@@ -1,26 +0,0 @@
-// sort Nominativ first and Dativ second to keep the convention that the first two morphemes identify the pronoun set
-const cases = ['n', 'd', 'a', 'g'];
-
-const morphemeByCase = (morphemeType) => {
-    return cases.map((caseAbbreviation) => `${morphemeType}_${caseAbbreviation}`);
-};
-
-const morphemeGroups = [
-    morphemeByCase('pronoun'),
-    morphemeByCase('possessive_determiner_f'),
-    morphemeByCase('possessive_determiner_m'),
-    morphemeByCase('possessive_determiner_n'),
-    morphemeByCase('possessive_determiner_x'),
-    morphemeByCase('possessive_determiner_pl'),
-    morphemeByCase('possessive_pronoun_f'),
-    morphemeByCase('possessive_pronoun_m'),
-    morphemeByCase('possessive_pronoun_n'),
-    morphemeByCase('possessive_pronoun_x'),
-    morphemeByCase('possessive_pronoun_pl'),
-    morphemeByCase('relative'),
-    morphemeByCase('demonstrative'),
-    ['pronoun_equal', 'possessive_pronoun_substantivized'],
-    ['adverb_because', 'adverb_back_then', 'adverb_by'],
-    ['adjective_back_then'],
-];
-export default morphemeGroups.flatMap((morphemeGroup) => morphemeGroup);
diff --git a/locale/de/pronouns/morphemes.ts b/locale/de/pronouns/morphemes.ts
new file mode 100644
index 000000000..e81dffdb9
--- /dev/null
+++ b/locale/de/pronouns/morphemes.ts
@@ -0,0 +1,28 @@
+// sort Nominativ first and Dativ second to keep the convention that the first two morphemes identify the pronoun set
+const cases = ['n', 'd', 'a', 'g'] as const;
+
+const morphemeByCase = <M extends string>(morphemeType: M): `${M}_${typeof cases[number]}`[] => {
+    return cases.map((caseAbbreviation) => `${morphemeType}_${caseAbbreviation}` as const);
+};
+
+export default [
+    ...morphemeByCase('pronoun'),
+    ...morphemeByCase('possessive_determiner_f'),
+    ...morphemeByCase('possessive_determiner_m'),
+    ...morphemeByCase('possessive_determiner_n'),
+    ...morphemeByCase('possessive_determiner_x'),
+    ...morphemeByCase('possessive_determiner_pl'),
+    ...morphemeByCase('possessive_pronoun_f'),
+    ...morphemeByCase('possessive_pronoun_m'),
+    ...morphemeByCase('possessive_pronoun_n'),
+    ...morphemeByCase('possessive_pronoun_x'),
+    ...morphemeByCase('possessive_pronoun_pl'),
+    ...morphemeByCase('relative'),
+    ...morphemeByCase('demonstrative'),
+    'pronoun_equal',
+    'possessive_pronoun_substantivized',
+    'adverb_because',
+    'adverb_back_then',
+    'adverb_by',
+    'adjective_back_then',
+] as const;
diff --git a/locale/en/pronouns/morphemes.js b/locale/en/pronouns/morphemes.js
deleted file mode 100644
index f082fdb28..000000000
--- a/locale/en/pronouns/morphemes.js
+++ /dev/null
@@ -1,7 +0,0 @@
-export default [
-    'pronoun_subject',
-    'pronoun_object',
-    'possessive_determiner',
-    'possessive_pronoun',
-    'reflexive',
-];
diff --git a/locale/_base/pronouns/morphemes.js b/locale/en/pronouns/morphemes.ts
similarity index 91%
rename from locale/_base/pronouns/morphemes.js
rename to locale/en/pronouns/morphemes.ts
index f082fdb28..0005ffc65 100644
--- a/locale/_base/pronouns/morphemes.js
+++ b/locale/en/pronouns/morphemes.ts
@@ -4,4 +4,4 @@ export default [
     'possessive_determiner',
     'possessive_pronoun',
     'reflexive',
-];
+] as const;
diff --git a/locale/eo/pronouns/morphemes.js b/locale/eo/pronouns/morphemes.ts
similarity index 76%
rename from locale/eo/pronouns/morphemes.js
rename to locale/eo/pronouns/morphemes.ts
index d0e5fa1c0..75f2dfc4a 100644
--- a/locale/eo/pronouns/morphemes.js
+++ b/locale/eo/pronouns/morphemes.ts
@@ -1,3 +1,3 @@
 export default [
     'pronoun_subject',
-];
+] as const;
diff --git a/locale/es/pronouns/morphemes.js b/locale/es/pronouns/morphemes.ts
similarity index 96%
rename from locale/es/pronouns/morphemes.js
rename to locale/es/pronouns/morphemes.ts
index b64e2969a..ec07ac116 100644
--- a/locale/es/pronouns/morphemes.js
+++ b/locale/es/pronouns/morphemes.ts
@@ -9,4 +9,4 @@ export default [
     'plural_direct_object_pronoun',
     'inflection',
     'inflection_c',
-];
+] as const;
diff --git a/locale/et/pronouns/morphemes.js b/locale/et/pronouns/morphemes.ts
similarity index 93%
rename from locale/et/pronouns/morphemes.js
rename to locale/et/pronouns/morphemes.ts
index 8447e057a..7e3e639f1 100644
--- a/locale/et/pronouns/morphemes.js
+++ b/locale/et/pronouns/morphemes.ts
@@ -6,4 +6,4 @@ export default [
     'reflexive',
     'thirdForm',
     'smallForm',
-];
+] as const;
diff --git a/locale/fr/pronouns/morphemes.js b/locale/fr/pronouns/morphemes.ts
similarity index 94%
rename from locale/fr/pronouns/morphemes.js
rename to locale/fr/pronouns/morphemes.ts
index 200f6abc8..d60cf8d33 100644
--- a/locale/fr/pronouns/morphemes.js
+++ b/locale/fr/pronouns/morphemes.ts
@@ -7,4 +7,4 @@ export default [
     'inflection_x',
     'inflection_e',
     'inflection_n',
-];
+] as const;
diff --git a/locale/gl/pronouns/morphemes.js b/locale/gl/pronouns/morphemes.ts
similarity index 95%
rename from locale/gl/pronouns/morphemes.js
rename to locale/gl/pronouns/morphemes.ts
index 108164f91..6ef801c59 100644
--- a/locale/gl/pronouns/morphemes.js
+++ b/locale/gl/pronouns/morphemes.ts
@@ -10,4 +10,4 @@ export default [
     'plural_indefinite_article',
     'inflection_c',
     'possessive',
-];
+] as const;
diff --git a/locale/he/pronouns/morphemes.js b/locale/he/pronouns/morphemes.ts
similarity index 91%
rename from locale/he/pronouns/morphemes.js
rename to locale/he/pronouns/morphemes.ts
index f082fdb28..0005ffc65 100644
--- a/locale/he/pronouns/morphemes.js
+++ b/locale/he/pronouns/morphemes.ts
@@ -4,4 +4,4 @@ export default [
     'possessive_determiner',
     'possessive_pronoun',
     'reflexive',
-];
+] as const;
diff --git a/locale/it/pronouns/morphemes.js b/locale/it/pronouns/morphemes.ts
similarity index 94%
rename from locale/it/pronouns/morphemes.js
rename to locale/it/pronouns/morphemes.ts
index 12e2c6b46..48c74d40e 100644
--- a/locale/it/pronouns/morphemes.js
+++ b/locale/it/pronouns/morphemes.ts
@@ -10,4 +10,4 @@ export default [
     'adjective',
     'past_participle',
     'h',
-];
+] as const;
diff --git a/locale/ja/pronouns/morphemes.js b/locale/ja/pronouns/morphemes.ts
similarity index 75%
rename from locale/ja/pronouns/morphemes.js
rename to locale/ja/pronouns/morphemes.ts
index dcf1ad36f..242a4c5e3 100644
--- a/locale/ja/pronouns/morphemes.js
+++ b/locale/ja/pronouns/morphemes.ts
@@ -1,3 +1,3 @@
 export default [
     'base_pronoun',
-];
+] as const;
diff --git a/locale/ko/pronouns/morphemes.js b/locale/ko/pronouns/morphemes.ts
similarity index 72%
rename from locale/ko/pronouns/morphemes.js
rename to locale/ko/pronouns/morphemes.ts
index d3c5e2de4..694ab022e 100644
--- a/locale/ko/pronouns/morphemes.js
+++ b/locale/ko/pronouns/morphemes.ts
@@ -1,3 +1,3 @@
 export default [
     'pronoun',
-];
+] as const;
diff --git a/locale/lad/pronouns/morphemes.js b/locale/lad/pronouns/morphemes.ts
similarity index 95%
rename from locale/lad/pronouns/morphemes.js
rename to locale/lad/pronouns/morphemes.ts
index 8949ab241..c9e30250f 100644
--- a/locale/lad/pronouns/morphemes.js
+++ b/locale/lad/pronouns/morphemes.ts
@@ -9,4 +9,4 @@ export default [
     'plural_direct_object_pronoun',
     'inflection',
     'inflection_l',
-];
+] as const;
diff --git a/locale/nl/pronouns/morphemes.js b/locale/nl/pronouns/morphemes.ts
similarity index 90%
rename from locale/nl/pronouns/morphemes.js
rename to locale/nl/pronouns/morphemes.ts
index 22a32cf75..c64248a41 100644
--- a/locale/nl/pronouns/morphemes.js
+++ b/locale/nl/pronouns/morphemes.ts
@@ -4,4 +4,4 @@ export default [
     'pronominal_poss',
     'predicative_poss',
     'dative',
-];
+] as const;
diff --git a/locale/no/pronouns/morphemes.js b/locale/no/pronouns/morphemes.ts
similarity index 88%
rename from locale/no/pronouns/morphemes.js
rename to locale/no/pronouns/morphemes.ts
index b01025fef..6959c58cd 100644
--- a/locale/no/pronouns/morphemes.js
+++ b/locale/no/pronouns/morphemes.ts
@@ -3,4 +3,4 @@ export default [
     'pronoun_object',
     'possessive',
     'reflexive',
-];
+] as const;
diff --git a/locale/pl/pronouns/morphemes.js b/locale/pl/pronouns/morphemes.ts
similarity index 97%
rename from locale/pl/pronouns/morphemes.js
rename to locale/pl/pronouns/morphemes.ts
index 58c652f0d..4ede8549f 100644
--- a/locale/pl/pronouns/morphemes.js
+++ b/locale/pl/pronouns/morphemes.ts
@@ -27,4 +27,4 @@ export default [
     'verb_go',
     'verb_o',
     'honorific',
-];
+] as const;
diff --git a/locale/pt/pronouns/morphemes.js b/locale/pt/pronouns/morphemes.ts
similarity index 96%
rename from locale/pt/pronouns/morphemes.js
rename to locale/pt/pronouns/morphemes.ts
index 5753b9f58..28d345eb2 100644
--- a/locale/pt/pronouns/morphemes.js
+++ b/locale/pt/pronouns/morphemes.ts
@@ -15,4 +15,4 @@ export default [
     'possessive',
     'demonstrative_ss',
     'demonstrative_st',
-];
+] as const;
diff --git a/locale/ro/pronouns/morphemes.js b/locale/ro/pronouns/morphemes.ts
similarity index 90%
rename from locale/ro/pronouns/morphemes.js
rename to locale/ro/pronouns/morphemes.ts
index 570b02aed..1ce984ff1 100644
--- a/locale/ro/pronouns/morphemes.js
+++ b/locale/ro/pronouns/morphemes.ts
@@ -4,4 +4,4 @@ export default [
     'strengthening',
     'first_article',
     'second_article',
-];
+] as const;
diff --git a/locale/ru/pronouns/morphemes.js b/locale/ru/pronouns/morphemes.ts
similarity index 96%
rename from locale/ru/pronouns/morphemes.js
rename to locale/ru/pronouns/morphemes.ts
index 27aafbd01..2aeae1667 100644
--- a/locale/ru/pronouns/morphemes.js
+++ b/locale/ru/pronouns/morphemes.ts
@@ -13,4 +13,4 @@ export default [
     'adjective',
     'possessive',
     'definitive',
-];
+] as const;
diff --git a/locale/sv/pronouns/morphemes.js b/locale/sv/pronouns/morphemes.ts
similarity index 87%
rename from locale/sv/pronouns/morphemes.js
rename to locale/sv/pronouns/morphemes.ts
index 6b4ec31e5..f2cbafd1b 100644
--- a/locale/sv/pronouns/morphemes.js
+++ b/locale/sv/pronouns/morphemes.ts
@@ -2,4 +2,4 @@ export default [
     'pronoun_nominative',
     'pronoun_object',
     'possessive',
-];
+] as const;
diff --git a/locale/tok/pronouns/morphemes.js b/locale/tok/pronouns/morphemes.ts
similarity index 72%
rename from locale/tok/pronouns/morphemes.js
rename to locale/tok/pronouns/morphemes.ts
index d3c5e2de4..694ab022e 100644
--- a/locale/tok/pronouns/morphemes.js
+++ b/locale/tok/pronouns/morphemes.ts
@@ -1,3 +1,3 @@
 export default [
     'pronoun',
-];
+] as const;
diff --git a/locale/tr/pronouns/morphemes.js b/locale/tr/pronouns/morphemes.js
deleted file mode 100644
index d6d1738de..000000000
--- a/locale/tr/pronouns/morphemes.js
+++ /dev/null
@@ -1 +0,0 @@
-export default [];
diff --git a/locale/tr/pronouns/morphemes.ts b/locale/tr/pronouns/morphemes.ts
new file mode 100644
index 000000000..8eb27f173
--- /dev/null
+++ b/locale/tr/pronouns/morphemes.ts
@@ -0,0 +1 @@
+export default [] as const;
diff --git a/locale/ua/pronouns/morphemes.js b/locale/ua/pronouns/morphemes.ts
similarity index 96%
rename from locale/ua/pronouns/morphemes.js
rename to locale/ua/pronouns/morphemes.ts
index fedc4ad58..f9aba9ad4 100644
--- a/locale/ua/pronouns/morphemes.js
+++ b/locale/ua/pronouns/morphemes.ts
@@ -12,4 +12,4 @@ export default [
     'adjective',
     'possessive',
     'definitive',
-];
+] as const;
diff --git a/locale/vi/pronouns/morphemes.js b/locale/vi/pronouns/morphemes.ts
similarity index 81%
rename from locale/vi/pronouns/morphemes.js
rename to locale/vi/pronouns/morphemes.ts
index 7be69cb9f..61468ec14 100644
--- a/locale/vi/pronouns/morphemes.js
+++ b/locale/vi/pronouns/morphemes.ts
@@ -1,4 +1,4 @@
 export default [
     '3rd_person',
     '2nd_person',
-];
+] as const;
diff --git a/locale/yi/pronouns/morphemes.js b/locale/yi/pronouns/morphemes.ts
similarity index 91%
rename from locale/yi/pronouns/morphemes.js
rename to locale/yi/pronouns/morphemes.ts
index a70187200..94249c85e 100644
--- a/locale/yi/pronouns/morphemes.js
+++ b/locale/yi/pronouns/morphemes.ts
@@ -6,4 +6,4 @@ export default [
     'article_n',
     'article_d',
     'article_a',
-];
+] as const;
diff --git a/locale/zh/pronouns/morphemes.js b/locale/zh/pronouns/morphemes.ts
similarity index 81%
rename from locale/zh/pronouns/morphemes.js
rename to locale/zh/pronouns/morphemes.ts
index 7be69cb9f..61468ec14 100644
--- a/locale/zh/pronouns/morphemes.js
+++ b/locale/zh/pronouns/morphemes.ts
@@ -1,4 +1,4 @@
 export default [
     '3rd_person',
     '2nd_person',
-];
+] as const;
diff --git a/new/backend/src/locales.ts b/new/backend/src/locales.ts
index ddb42c59f..7a058c2d5 100644
--- a/new/backend/src/locales.ts
+++ b/new/backend/src/locales.ts
@@ -369,7 +369,7 @@ export class Locale {
             text: "data:image/svg+xml," + encodeURIComponent(logoSource.text),
         };
 
-        this._morphemes = (await this.importFile(["pronouns/morphemes.js"]))
+        this._morphemes = (await this.importFile(["pronouns/morphemes.ts"]))
             .default as string[];
         this._pronouns = [];
         this._pronounsByAlias = {};
diff --git a/plugins/data.d.ts b/plugins/data.d.ts
deleted file mode 100644
index 540622fd1..000000000
--- a/plugins/data.d.ts
+++ /dev/null
@@ -1,64 +0,0 @@
-import type { Config } from '../locale/config.ts';
-import type { Translations } from '../locale/translations.ts';
-
-export interface PronounsData<M extends string[]> {
-    key: string;
-    description: string;
-    normative: string;
-    [morpheme: M]: string | null;
-    plural: string;
-    pluralHonorific: string;
-    pronounceable: string;
-    history?: string;
-    thirdForm?: M;
-    smallForm?: M;
-    sourcesInfo?: string;
-    hidden?: boolean;
-}
-
-export interface PronounExamplesData {
-    singular: string;
-    plural?: string;
-    isHonorific?: boolean;
-}
-
-export interface NounTemplatesData {
-    masc: string;
-    fem: string;
-    neutr: string;
-    mascPl: string;
-    femPl: string;
-    neutrPl: string;
-}
-
-declare namespace Data {
-    declare module '*/config.suml' {
-        declare const config: Config;
-        export default config;
-    }
-
-    declare module '*/translations.suml' {
-        declare const translations: Translations;
-        export default translations;
-    }
-
-    declare module '*/pronouns/pronouns.tsv' {
-        declare const data: PronounsData[];
-        export default data;
-    }
-
-    declare module '*/pronouns/examples.tsv' {
-        declare const data: PronounExamplesData[];
-        export default data;
-    }
-
-    declare module '*/nouns/nounTemplates.tsv' {
-        declare const data: NounTemplatesData[];
-        export default data;
-    }
-
-    declare module '*.tsv' {
-        declare const data: Record<string, any>[];
-        export default data;
-    }
-}
diff --git a/routes/pronouns.vue b/routes/pronouns.vue
index 19a832d3b..857b37958 100644
--- a/routes/pronouns.vue
+++ b/routes/pronouns.vue
@@ -280,7 +280,7 @@ import Vue from 'vue';
 import { examples, pronouns, pronounLibrary } from '../src/data.ts';
 import { ExampleCategory, ExamplePart, Pronoun } from '../src/classes.ts';
 import Compressor from '../src/compressor.js';
-import MORPHEMES from '../data/pronouns/morphemes.js';
+import MORPHEMES from '../data/pronouns/morphemes.ts';
 import { mapState } from 'vuex';
 import Suggested from '../data/pronouns/Suggested.vue';
 import type { PronounLibrary, Example } from '../src/classes.ts';
diff --git a/src/buildPronoun.ts b/src/buildPronoun.ts
index 1581eb2c0..bc80ecb2f 100644
--- a/src/buildPronoun.ts
+++ b/src/buildPronoun.ts
@@ -1,9 +1,10 @@
 import { Pronoun } from './classes.ts';
 import Compressor from './compressor.js';
 import { buildDict, isEmoji, unescapeControlSymbols } from './helpers.ts';
-import MORPHEMES from '../data/pronouns/morphemes.js';
+import MORPHEMES from '../data/pronouns/morphemes.ts';
 import type { Config, NullPronounsConfig } from '../locale/config.ts';
 import type { Translator } from './translator.js';
+import type { PronounData } from '../locale/data.ts';
 
 export const addAliasesToPronouns = (pronouns: Record<string, Pronoun>): Record<string, Pronoun> => {
     const pronounsWithAliases: Record<string, Pronoun> = {};
@@ -274,7 +275,7 @@ export const buildPronoun = (
 
 export const parsePronouns = (
     config: Config,
-    pronounsRaw: Record<string, any>[],
+    pronounsRaw: PronounData<string>[],
 ): Record<string, Pronoun> => {
     return buildDict(function* () {
         for (const t of pronounsRaw) {
diff --git a/src/classes.ts b/src/classes.ts
index 6789b1e86..1c7ad7b7c 100644
--- a/src/classes.ts
+++ b/src/classes.ts
@@ -1,5 +1,5 @@
 import { buildDict, buildList, capitalise, escapeControlSymbols, escapePronunciationString } from './helpers.ts';
-import MORPHEMES from '../data/pronouns/morphemes.js';
+import MORPHEMES from '../data/pronouns/morphemes.ts';
 import type { Translator } from './translator.js';
 import type { Config } from '../locale/config.ts';
 
@@ -388,7 +388,7 @@ export class Pronoun {
     pronounceable: boolean;
     thirdForm: string | null;
     smallForm: string | null;
-    sourcesInfo: Record<keyof any, string> | null;
+    sourcesInfo: string | null;
     hidden: boolean;
     static DESCRIPTION_MAXLENGTH = 64;
 
@@ -405,7 +405,7 @@ export class Pronoun {
         pronounceable: boolean = true,
         thirdForm: string | null = null,
         smallForm: string | null = null,
-        sourcesInfo = null,
+        sourcesInfo: string | null = null,
         hidden: boolean = false,
     ) {
         this.config = config;
@@ -437,7 +437,7 @@ export class Pronoun {
     nameOptions(): string[] {
         const options: Set<string> = new Set();
         const optionsN = (this.morphemes[MORPHEMES[0]] || '').split('&');
-        if (MORPHEMES.length === 1) {
+        if (MORPHEMES.length as number === 1) {
             return optionsN;
         }
         const optionsG: string[] = (this.morphemes[MORPHEMES[1]] || '').split('&');
diff --git a/test/buildPronoun.test.ts b/test/buildPronoun.test.ts
index 9bdd35292..0f5ae9255 100644
--- a/test/buildPronoun.test.ts
+++ b/test/buildPronoun.test.ts
@@ -16,7 +16,7 @@ const translations = {
 const translator = new Translator(translations, translations, []);
 
 // workaround to be independent of the current selected locale
-jest.unstable_mockModule('../data/pronouns/morphemes.js', () => {
+jest.unstable_mockModule('../data/pronouns/morphemes.ts', () => {
     return {
         default: ['pronoun_subject', 'pronoun_object', 'possessive_determiner', 'possessive_pronoun', 'reflexive'],
     };
diff --git a/test/locales/data.test.ts b/test/locales/data.test.ts
index 66de4bb4a..c221fc8fa 100644
--- a/test/locales/data.test.ts
+++ b/test/locales/data.test.ts
@@ -6,7 +6,7 @@ import { Example, gendersWithNumerus } from '../../src/classes.ts';
 import type { ExpectationResult } from 'expect';
 import { loadSumlFromBase } from '../../server/loader.ts';
 import type { Config } from '../../locale/config.ts';
-import type { NounTemplatesData, PronounExamplesData, PronounsData } from '../../plugins/data';
+import type { NounTemplatesData, PronounExamplesData, PronounData } from '../../locale/data.ts';
 
 const __dirname = new URL('.', import.meta.url).pathname;
 
@@ -44,8 +44,8 @@ describe.each(allLocales)('data files of $code', ({ code }) => {
     const nounTemplates = loadTsv<NounTemplatesData>(`${__dirname}/../../locale/${code}/nouns/nounTemplates.tsv`);
 
     test('pronouns/pronouns.tsv match schema', async () => {
-        const { default: MORPHEMES } = await import(`../../locale/${code}/pronouns/morphemes.js`);
-        const pronouns = loadTsv<PronounsData<string[]>>(`${__dirname}/../../locale/${code}/pronouns/pronouns.tsv`);
+        const { default: MORPHEMES } = await import(`../../locale/${code}/pronouns/morphemes.ts`);
+        const pronouns = loadTsv<PronounData<string>>(`${__dirname}/../../locale/${code}/pronouns/pronouns.tsv`);
         if (pronouns.length === 0) {
             return;
         }
@@ -80,7 +80,7 @@ describe.each(allLocales)('data files of $code', ({ code }) => {
         expect(actual).toEqual(required);
     });
     test('pronouns/examples.tsv contain valid morphemes', async () => {
-        const { default: MORPHEMES } = await import(`../../locale/${code}/pronouns/morphemes.js`);
+        const { default: MORPHEMES } = await import(`../../locale/${code}/pronouns/morphemes.ts`);
         for (const example of examples) {
             expect(example.singular).toHaveValidMorphemes(MORPHEMES);
             if (example.plural) {