diff --git a/server/tests/test_signal_hooks.py b/server/tests/test_signal_hooks.py
new file mode 100644
index 0000000..ff831ed
--- /dev/null
+++ b/server/tests/test_signal_hooks.py
@@ -0,0 +1,27 @@
+from unittest.mock import patch
+
+from tga.signal_hooks import generate_doi
+
+
+@patch("tga.signal_hooks._generate_short_unique_id")
+def test_generate_doi_existing_doi(mock_generate_short_unique_id):
+    item = {"extra": {"doi": "existing_doi"}}
+    updates = {}
+    generate_doi(None, item, updates)
+    assert item["extra"]["doi"] == "existing_doi"
+    assert "extra" not in updates
+
+    item = {"extra": {}}
+    updates = {}
+    generate_doi(None, item, updates)
+    assert item["extra"]["doi"] is not None
+    assert item["extra"]["doi"] == updates["extra"]["doi"]
+
+
+@patch("tga.signal_hooks._generate_short_unique_id")
+def test_generate_doi_new_doi(mock_generate_short_unique_id):
+    item = {"extra": {}}
+    updates = {}
+    generate_doi(None, item, updates)
+    assert item["extra"]["doi"] is not None
+    assert item["extra"]["doi"] == updates["extra"]["doi"]
diff --git a/server/tga/signal_hooks.py b/server/tga/signal_hooks.py
index 9d064f8..a8c0ed9 100644
--- a/server/tga/signal_hooks.py
+++ b/server/tga/signal_hooks.py
@@ -13,8 +13,10 @@
 
 def generate_doi(_sender, item, updates):
     """Assign a DOI to this item if one does not already exist"""
-
     item.setdefault("extra", {})
+    if item["extra"].get("doi"):
+        return
+
     updates.setdefault("extra", {})
     updates["extra"]["doi"] = updates["extra"].get("doi") or item["extra"].get("doi") or _generate_short_unique_id()
     item["extra"]["doi"] = updates["extra"]["doi"]