diff --git a/spec/Bundle.ts b/spec/Bundle.ts
index dcb8ff1..ac9d321 100644
--- a/spec/Bundle.ts
+++ b/spec/Bundle.ts
@@ -22,7 +22,7 @@ describe("Bundle", () => {
 			// @ts-expect-error
 			expect(() => new Bundle()).toThrowError(
 				Error,
-				"Cannot build Bundle. MimeType is missing",
+				Messages.BUNDLE.MIME_TYPE_MISSING,
 			);
 		});
 
diff --git a/src/Bundle.ts b/src/Bundle.ts
index 2ec1f4f..5337965 100644
--- a/src/Bundle.ts
+++ b/src/Bundle.ts
@@ -21,7 +21,7 @@ export default class Bundle {
 
 	constructor(public mimeType: `${Mime.type}/${Mime.subtype}`) {
 		if (!mimeType) {
-			throw new Error("Cannot build Bundle. MimeType is missing");
+			throw new Error(Messages.BUNDLE.MIME_TYPE_MISSING);
 		}
 	}
 
diff --git a/src/messages.ts b/src/messages.ts
index c20742d..e2ac6c7 100644
--- a/src/messages.ts
+++ b/src/messages.ts
@@ -74,6 +74,7 @@ export const MODELS = {
 } as const;
 
 export const BUNDLE = {
+	MIME_TYPE_MISSING: "Cannot build Bundle. MimeType is missing",
 	CLOSED: "Cannot add file. Bundle is closed.",
 } as const;