diff --git a/src/Bundle.ts b/src/Bundle.ts
index b6dc33f..ec5ecca 100644
--- a/src/Bundle.ts
+++ b/src/Bundle.ts
@@ -1,7 +1,7 @@
 import { Readable, Stream } from "node:stream";
-import * as Messages from "./messages";
-import { toArray as zipToArray } from "do-not-zip";
 import { Buffer } from "node:buffer";
+import { toArray as zipToArray } from "do-not-zip";
+import * as Messages from "./messages.js";
 
 export const filesSymbol = Symbol("bundleFiles");
 export const freezeSymbol = Symbol("bundleFreeze");
diff --git a/src/FieldsArray.ts b/src/FieldsArray.ts
index c4c635c..84f169d 100644
--- a/src/FieldsArray.ts
+++ b/src/FieldsArray.ts
@@ -1,7 +1,7 @@
-import type PKPass from "./PKPass";
-import * as Schemas from "./schemas";
-import * as Utils from "./utils";
-import * as Messages from "./messages";
+import type PKPass from "./PKPass.js";
+import * as Schemas from "./schemas/index.js";
+import * as Utils from "./utils.js";
+import * as Messages from "./messages.js";
 
 /**
  * Class to represent lower-level keys pass fields
diff --git a/src/PKPass.ts b/src/PKPass.ts
index 9a7e57a..3e5e1b5 100644
--- a/src/PKPass.ts
+++ b/src/PKPass.ts
@@ -1,14 +1,14 @@
 import { Stream } from "node:stream";
 import { Buffer } from "node:buffer";
 import path from "node:path";
-import FieldsArray from "./FieldsArray";
-import Bundle, { filesSymbol } from "./Bundle";
-import getModelFolderContents from "./getModelFolderContents";
-import * as Schemas from "./schemas";
-import * as Signature from "./Signature";
-import * as Strings from "./StringsUtils";
-import * as Utils from "./utils";
-import * as Messages from "./messages";
+import FieldsArray from "./FieldsArray.js";
+import Bundle, { filesSymbol } from "./Bundle.js";
+import getModelFolderContents from "./getModelFolderContents.js";
+import * as Schemas from "./schemas/index.js";
+import * as Signature from "./Signature.js";
+import * as Strings from "./StringsUtils.js";
+import * as Utils from "./utils.js";
+import * as Messages from "./messages.js";
 
 const propsSymbol = Symbol("props");
 const localizationSymbol = Symbol("pass.l10n");
diff --git a/src/Signature.ts b/src/Signature.ts
index 7d17cf6..3f3d703 100644
--- a/src/Signature.ts
+++ b/src/Signature.ts
@@ -1,5 +1,5 @@
 import forge from "node-forge";
-import type * as Schemas from "./schemas";
+import type * as Schemas from "./schemas/index.js";
 import { Buffer } from "node:buffer";
 
 /**
diff --git a/src/getModelFolderContents.ts b/src/getModelFolderContents.ts
index 1867a51..8c45c05 100644
--- a/src/getModelFolderContents.ts
+++ b/src/getModelFolderContents.ts
@@ -1,8 +1,8 @@
 import * as path from "node:path";
-import * as Utils from "./utils";
-import * as Messages from "./messages";
 import { promises as fs } from "node:fs";
 import type { Buffer } from "node:buffer";
+import * as Utils from "./utils.js";
+import * as Messages from "./messages.js";
 
 /**
  * Reads the model folder contents
diff --git a/src/index.ts b/src/index.ts
index 2eaee24..7f62b66 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,4 @@
-export { default as PKPass } from "./PKPass";
+export { default as PKPass } from "./PKPass.js";
 
 // ***************************************** //
 // *** Exporting only schemas interfaces *** //
@@ -15,4 +15,4 @@ export type {
 	TransitType,
 	Personalize,
 	OverridablePassProps,
-} from "./schemas";
+} from "./schemas/index.js";
diff --git a/src/schemas/Field.ts b/src/schemas/Field.ts
index 28a9bf2..3387a90 100644
--- a/src/schemas/Field.ts
+++ b/src/schemas/Field.ts
@@ -1,5 +1,5 @@
 import Joi from "joi";
-import { Semantics } from "./Semantics";
+import { Semantics } from "./Semantics.js";
 
 export type PKDataDetectorType =
 	| "PKDataDetectorTypePhoneNumber"
diff --git a/src/schemas/PassFields.ts b/src/schemas/PassFields.ts
index a148e4c..331441c 100644
--- a/src/schemas/PassFields.ts
+++ b/src/schemas/PassFields.ts
@@ -1,5 +1,5 @@
 import Joi from "joi";
-import { Field, FieldWithRow } from "./Field";
+import { Field, FieldWithRow } from "./Field.js";
 
 export type TransitType =
 	| "PKTransitTypeAir"
diff --git a/src/schemas/SemanticTagType.ts b/src/schemas/SemanticTagType.ts
index 0eda385..60050a2 100644
--- a/src/schemas/SemanticTagType.ts
+++ b/src/schemas/SemanticTagType.ts
@@ -1,5 +1,5 @@
 import Joi from "joi";
-import { RGB_HEX_COLOR_REGEX } from "./regexps";
+import { RGB_HEX_COLOR_REGEX } from "./regexps.js";
 
 /**
  * These couple of structures are organized alphabetically,
diff --git a/src/schemas/Semantics.ts b/src/schemas/Semantics.ts
index 458f96b..a30d592 100644
--- a/src/schemas/Semantics.ts
+++ b/src/schemas/Semantics.ts
@@ -1,5 +1,5 @@
 import Joi from "joi";
-import * as SemanticTagType from "./SemanticTagType";
+import * as SemanticTagType from "./SemanticTagType.js";
 
 /**
  * For a better description of every single field,
diff --git a/src/schemas/index.ts b/src/schemas/index.ts
index 90320ee..4b21743 100644
--- a/src/schemas/index.ts
+++ b/src/schemas/index.ts
@@ -1,26 +1,26 @@
-export * from "./Barcode";
-export * from "./Beacon";
-export * from "./Location";
-export * from "./Field";
-export * from "./NFC";
-export * from "./Semantics";
-export * from "./PassFields";
-export * from "./Personalize";
-export * from "./Certificates";
+export * from "./Barcode.js";
+export * from "./Beacon.js";
+export * from "./Location.js";
+export * from "./Field.js";
+export * from "./NFC.js";
+export * from "./Semantics.js";
+export * from "./PassFields.js";
+export * from "./Personalize.js";
+export * from "./Certificates.js";
 
 import Joi from "joi";
 import type { Buffer } from "node:buffer";
 
-import { Barcode } from "./Barcode";
-import { Location } from "./Location";
-import { Beacon } from "./Beacon";
-import { NFC } from "./NFC";
-import { PassFields, TransitType } from "./PassFields";
-import { Semantics } from "./Semantics";
-import { CertificatesSchema } from "./Certificates";
+import { Barcode } from "./Barcode.js";
+import { Location } from "./Location.js";
+import { Beacon } from "./Beacon.js";
+import { NFC } from "./NFC.js";
+import { PassFields, TransitType } from "./PassFields.js";
+import { Semantics } from "./Semantics.js";
+import { CertificatesSchema } from "./Certificates.js";
 
-import * as Messages from "../messages";
-import { RGB_HEX_COLOR_REGEX, URL_REGEX } from "./regexps";
+import * as Messages from "../messages.js";
+import { RGB_HEX_COLOR_REGEX, URL_REGEX } from "./regexps.js";
 
 export type PreferredStyleSchemes = ("posterEventTicket" | "eventTicket")[];
 
diff --git a/src/utils.ts b/src/utils.ts
index 25aae57..f7ba228 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,5 +1,5 @@
-import * as Messages from "./messages";
-import type Bundle from "./Bundle";
+import * as Messages from "./messages.js";
+import type Bundle from "./Bundle.js";
 
 /**
  * Converts a date to W3C / UTC string