diff --git a/Sources/Navigator/Audiobook/PublicationMediaLoader.swift b/Sources/Navigator/Audiobook/PublicationMediaLoader.swift
index 714b5df4e..bba1fdb41 100644
--- a/Sources/Navigator/Audiobook/PublicationMediaLoader.swift
+++ b/Sources/Navigator/Audiobook/PublicationMediaLoader.swift
@@ -84,7 +84,7 @@ final class PublicationMediaLoader: NSObject, AVAssetResourceLoaderDelegate {
     /// Terminates and removes the given loading request, cancelling it if necessary.
     private func finishRequest(_ request: AVAssetResourceLoadingRequest) {
         guard
-            let href = request.href,
+            let href = request.request.url?.audioHREF,
             var reqs = requests[href],
             let index = reqs.firstIndex(where: { req, _ in req == request })
         else {
@@ -106,7 +106,7 @@ final class PublicationMediaLoader: NSObject, AVAssetResourceLoaderDelegate {
     // MARK: - AVAssetResourceLoaderDelegate
 
     func resourceLoader(_ resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool {
-        guard let href = loadingRequest.href else {
+        guard let href = loadingRequest.request.url?.audioHREF else {
             return false
         }
 
@@ -163,22 +163,16 @@ final class PublicationMediaLoader: NSObject, AVAssetResourceLoaderDelegate {
 
 private let schemePrefix = "r2"
 
-private extension AVAssetResourceLoadingRequest {
-    var href: String? {
-        guard let url = request.url?.absoluteURL, url.scheme.rawValue.hasPrefix(schemePrefix) == true else {
+extension URL {
+    var audioHREF: String? {
+        guard let url = absoluteURL, url.scheme.rawValue.hasPrefix(schemePrefix) == true else {
             return nil
         }
 
         // The URL can be either:
-        // * r2file://directory/local-file.mp3
+        // * r2:relative/file.mp3
+        // * r2file:///directory/local-file.mp3
         // * r2http(s)://domain.com/external-file.mp3
-        switch url.scheme.rawValue {
-        case "r2file", "r2":
-            return url.path
-        case "r2http", "r2https":
-            return url.string.removingPrefix(schemePrefix)
-        default:
-            return nil
-        }
+        return url.string.removingPrefix(schemePrefix).removingPrefix(":")
     }
 }
diff --git a/Tests/NavigatorTests/Audio/PublicationMediaLoaderTests.swift b/Tests/NavigatorTests/Audio/PublicationMediaLoaderTests.swift
new file mode 100644
index 000000000..327c83203
--- /dev/null
+++ b/Tests/NavigatorTests/Audio/PublicationMediaLoaderTests.swift
@@ -0,0 +1,30 @@
+//
+//  Copyright 2024 Readium Foundation. All rights reserved.
+//  Use of this source code is governed by the BSD-style license
+//  available in the top-level LICENSE file of the project.
+//
+
+@testable import R2Navigator
+import XCTest
+
+class PublicationMediaLoaderTests: XCTestCase {
+    func testURLToHREF() {
+        XCTAssertEqual(URL(string: "r2:relative/file.mp3")!.audioHREF, "relative/file.mp3")
+        XCTAssertEqual(URL(string: "r2:/absolute/file.mp3")!.audioHREF, "/absolute/file.mp3")
+        XCTAssertEqual(URL(string: "r2file:///directory/file.mp3")!.audioHREF, "file:///directory/file.mp3")
+        XCTAssertEqual(URL(string: "r2http:///domain.com/file.mp3")!.audioHREF, "http:///domain.com/file.mp3")
+        XCTAssertEqual(URL(string: "r2https:///domain.com/file.mp3")!.audioHREF, "https:///domain.com/file.mp3")
+
+        // Encoded characters
+        XCTAssertEqual(URL(string: "r2:relative/a%20file.mp3")!.audioHREF, "relative/a%20file.mp3")
+        XCTAssertEqual(URL(string: "r2:/absolute/a%20file.mp3")!.audioHREF, "/absolute/a%20file.mp3")
+        XCTAssertEqual(URL(string: "r2file:///directory/a%20file.mp3")!.audioHREF, "file:///directory/a%20file.mp3")
+        XCTAssertEqual(URL(string: "r2http:///domain.com/a%20file.mp3")!.audioHREF, "http:///domain.com/a%20file.mp3")
+        XCTAssertEqual(URL(string: "r2https:///domain.com/a%20file.mp3")!.audioHREF, "https:///domain.com/a%20file.mp3")
+
+        // Ignores if the r2 prefix is missing.
+        XCTAssertNil(URL(string: "relative/file.mp3")!.audioHREF)
+        XCTAssertNil(URL(string: "file:///directory/file.mp3")!.audioHREF)
+        XCTAssertNil(URL(string: "http:///domain.com/file.mp3")!.audioHREF)
+    }
+}