diff --git a/google-cloud-storage/src/main/java/com/google/cloud/storage/spi/v1/HttpStorageRpc.java b/google-cloud-storage/src/main/java/com/google/cloud/storage/spi/v1/HttpStorageRpc.java
index 23251edc5..11d4b9876 100644
--- a/google-cloud-storage/src/main/java/com/google/cloud/storage/spi/v1/HttpStorageRpc.java
+++ b/google-cloud-storage/src/main/java/com/google/cloud/storage/spi/v1/HttpStorageRpc.java
@@ -956,6 +956,10 @@ public String open(String signedURL) {
       HttpHeaders requestHeaders = httpRequest.getHeaders();
       requestHeaders.set("X-Upload-Content-Type", "");
       requestHeaders.set("x-goog-resumable", "start");
+      // Using the x-goog-api-client header causes a signature mismatch with signed URLs generated
+      // outside the Java storage client
+      requestHeaders.remove("x-goog-api-client");
+
       HttpResponse response = httpRequest.execute();
       if (response.getStatusCode() != 201) {
         GoogleJsonError error = new GoogleJsonError();
diff --git a/google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java b/google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java
index 305580204..7ed1239b2 100644
--- a/google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java
+++ b/google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java
@@ -3421,15 +3421,23 @@ public void testUploadUsingSignedURL() throws Exception {
     String blobName = "test-signed-url-upload";
     BlobInfo blob = BlobInfo.newBuilder(BUCKET, blobName).build();
     assertNotNull(storage.create(blob));
+    Map<String, String> extensionHeaders = new HashMap<>();
+    extensionHeaders.put("x-goog-resumable", "start");
     for (Storage.SignUrlOption urlStyle :
         Arrays.asList(
             Storage.SignUrlOption.withPathStyle(),
             Storage.SignUrlOption.withVirtualHostedStyle())) {
       URL signUrl =
           storage.signUrl(
-              blob, 1, TimeUnit.HOURS, Storage.SignUrlOption.httpMethod(HttpMethod.POST), urlStyle);
+              blob,
+              1,
+              TimeUnit.HOURS,
+              Storage.SignUrlOption.httpMethod(HttpMethod.POST),
+              Storage.SignUrlOption.withExtHeaders(extensionHeaders),
+              urlStyle);
       byte[] bytesArrayToUpload = BLOB_STRING_CONTENT.getBytes();
-      try (WriteChannel writer = storage.writer(signUrl)) {
+      Storage unauthenticatedStorage = StorageOptions.getUnauthenticatedInstance().getService();
+      try (WriteChannel writer = unauthenticatedStorage.writer(signUrl)) {
         writer.write(ByteBuffer.wrap(bytesArrayToUpload, 0, bytesArrayToUpload.length));
       }