diff --git a/src/sentry/api/endpoints/debug_files.py b/src/sentry/api/endpoints/debug_files.py
index fb6e190fd102..4d9f736bdce7 100644
--- a/src/sentry/api/endpoints/debug_files.py
+++ b/src/sentry/api/endpoints/debug_files.py
@@ -858,11 +858,15 @@ def _clone_proguard_debug_file_for_reupload(
         }
 
     meta = build_proguard_reupload_dif_meta(debug_file, requested_debug_id)
-    if not debug_file.uses_objectstore_for_read():
+    if debug_file.storage_path is None:
         assert debug_file.file is not None
         dif, created = create_dif_from_id(project, meta, file=debug_file.file)
     else:
-        source_fileobj = debug_file.get_file()
+        response = debug_file._get_objectstore_session().get(debug_file.storage_path)
+        if response is None:
+            raise FileNotFoundError("Debug file does not exist in Objectstore")
+
+        source_fileobj = response.payload
         try:
             # Spool into a temporary file to get a seekable stream.
             with tempfile.TemporaryFile() as tmp:
diff --git a/tests/sentry/api/endpoints/test_dif_assemble.py b/tests/sentry/api/endpoints/test_dif_assemble.py
index 1865d61a0085..a1cd7c4a214d 100644
--- a/tests/sentry/api/endpoints/test_dif_assemble.py
+++ b/tests/sentry/api/endpoints/test_dif_assemble.py
@@ -437,6 +437,59 @@ def test_reuses_existing_proguard_file_with_new_debug_id(self) -> None:
             assert first_dif.file_id == second_dif.file_id
             assert File.objects.filter(type="project.dif", checksum=checksum).count() == 1
 
+    def test_objectstore_assemble_clones_existing_proguard_to_new_objectstore_file(self) -> None:
+        file_contents = b"proguard mapping"
+        checksum = sha1(file_contents).hexdigest()
+        get_chunk_upload_session(self.organization.id).put(file_contents, key=checksum)
+        chunks = [checksum]
+
+        with self.feature(
+            {
+                "organizations:objectstore-debugfiles-exclusive-write": True,
+                "organizations:objectstore-debugfiles-write": False,
+                "organizations:objectstore-debugfiles-read": True,
+            }
+        ):
+            assemble_dif(
+                project_id=self.project.id,
+                name="/proguard/mapping-00000000-0000-0000-0000-000000000000.txt",
+                checksum=checksum,
+                chunks=chunks,
+                use_objectstore=True,
+            )
+
+            first_dif = ProjectDebugFile.objects.get(
+                project_id=self.project.id,
+                debug_id="00000000-0000-0000-0000-000000000000",
+            )
+
+            response = self.client.post(
+                self.url,
+                data={
+                    checksum: {
+                        "name": "/proguard/mapping-11111111-1111-1111-1111-111111111111.txt",
+                        "chunks": chunks,
+                    }
+                },
+                HTTP_AUTHORIZATION=f"Bearer {self.token.token}",
+            )
+
+            assert response.status_code == 200, response.content
+            assert response.data[checksum]["state"] == ChunkFileState.OK
+            assert response.data[checksum]["dif"]["uuid"] == "11111111-1111-1111-1111-111111111111"
+
+            second_dif = ProjectDebugFile.objects.get(
+                project_id=self.project.id,
+                debug_id="11111111-1111-1111-1111-111111111111",
+            )
+
+            assert first_dif.file_id is None
+            assert second_dif.file_id is None
+            assert first_dif.storage_path is not None
+            assert second_dif.storage_path is not None
+            assert first_dif.storage_path != second_dif.storage_path
+            assert File.objects.filter(type="project.dif", checksum=checksum).count() == 0
+
     def test_reupload_proguard_with_same_debug_id_is_idempotent(self) -> None:
         file_contents = b"proguard mapping"
         checksum = sha1(file_contents).hexdigest()
@@ -590,6 +643,7 @@ def test_clone_dual_written_source_to_file(self) -> None:
         )
         assert first_dif.file_id is not None
         assert first_dif.storage_path is not None
+        assert not first_dif.uses_objectstore_for_read()
 
         with self.feature({"organizations:objectstore-debugfiles-write": False}):
             response = self._clone_request(checksum, chunks)
@@ -604,5 +658,37 @@ def test_clone_dual_written_source_to_file(self) -> None:
         )
         # The source stays Objectstore-backed; the clone is written as a File.
         assert second_dif.file_id is not None
+        assert second_dif.file_id != first_dif.file_id
         assert second_dif.storage_path is None
         assert second_dif.get_file().read() == file_contents
+
+    def test_clone_file_backed_source_to_objectstore_exclusive(self) -> None:
+        file_contents = b"proguard mapping"
+        checksum = sha1(file_contents).hexdigest()
+        blob = FileBlob.from_file_with_organization(ContentFile(file_contents), self.organization)
+        chunks = [blob.checksum]
+
+        with self.feature({"organizations:objectstore-debugfiles-write": False}):
+            self._assemble_source(checksum, chunks)
+
+        first_dif = ProjectDebugFile.objects.get(
+            project_id=self.project.id,
+            debug_id="00000000-0000-0000-0000-000000000000",
+        )
+        assert first_dif.file_id is not None
+        assert first_dif.storage_path is None
+
+        with self.feature("organizations:objectstore-debugfiles-exclusive-write"):
+            response = self._clone_request(checksum, chunks)
+
+        assert response.status_code == 200, response.content
+        assert response.data[checksum]["state"] == ChunkFileState.OK
+
+        second_dif = ProjectDebugFile.objects.get(
+            project_id=self.project.id,
+            debug_id="11111111-1111-1111-1111-111111111111",
+        )
+        assert second_dif.file_id is None
+        assert second_dif.storage_path is not None
+        assert second_dif.get_file().read() == file_contents
+        assert File.objects.filter(type="project.dif", checksum=checksum).count() == 1