diff --git a/backend/leads/services.py b/backend/leads/services.py
index 391ce101..3236330b 100644
--- a/backend/leads/services.py
+++ b/backend/leads/services.py
@@ -22,7 +22,8 @@ def conversion_account_name(lead):
     """The name of the account a conversion files ``lead`` under."""
     if lead.company_name:
         return lead.company_name
-    return f"{lead.first_name} {lead.last_name}"
+    parts = [(p or "").strip() for p in (lead.first_name, lead.last_name)]
+    return " ".join(p for p in parts if p) or f"Lead {lead.id}"
 
 
 def conversion_refusal(request, lead):
@@ -33,7 +34,7 @@ def conversion_refusal(request, lead):
     open would make it theirs (and every contact linked to it). That is
     refused. An account they can open, or no match at all, is fine.
 
-    ``lead`` only needs ``company_name``, ``first_name`` and ``last_name``, so
+    ``lead`` only needs ``id``, ``company_name``, ``first_name`` and ``last_name``, so
     a view can ask with the values a save is about to write, before writing.
     """
     matches = Account.objects.filter(
diff --git a/backend/leads/tests/test_convert_requires_account_access.py b/backend/leads/tests/test_convert_requires_account_access.py
index f87e31ef..d2e424c8 100644
--- a/backend/leads/tests/test_convert_requires_account_access.py
+++ b/backend/leads/tests/test_convert_requires_account_access.py
@@ -25,7 +25,7 @@ from accounts.models import Account
 from common.models import Comment
 from contacts.models import Contact
 from leads.models import Lead
-from leads.services import convert_lead_to_account
+from leads.services import conversion_account_name, convert_lead_to_account
 from opportunity.models import Opportunity
 
 pytestmark = pytest.mark.django_db
@@ -314,3 +314,35 @@ class TestAllowedWithAccountAccess:
         account = Account.objects.get(id=response.json()["account_id"])
         assert account.name == "Elsewhere Inc"
         assert set(hidden_account.assigned_to.all()) == {admin_profile}
+
+
+class TestConversionAccountName:
+    @pytest.mark.parametrize(
+        "first_name, last_name, expected",
+        [
+            ("Ada", None, "Ada"),
+            (None, "Smith", "Smith"),
+            ("Ada", "Smith", "Ada Smith"),
+            (" ", "Smith", "Smith"),
+            (" Ada ", " ", "Ada"),
+        ],
+    )
+    def test_account_name_skips_missing_name_parts(
+        self, first_name, last_name, expected
+    ):
+        lead = SimpleNamespace(
+            id="abc", company_name=None, first_name=first_name, last_name=last_name
+        )
+        assert conversion_account_name(lead) == expected
+
+    def test_account_name_for_nameless_lead_has_no_none(self):
+        lead = SimpleNamespace(
+            id="abc", company_name=None, first_name=None, last_name=None
+        )
+        assert conversion_account_name(lead) == "Lead abc"
+
+    def test_account_name_for_whitespace_only_names_falls_back(self):
+        lead = SimpleNamespace(
+            id="abc", company_name=None, first_name=" ", last_name=" "
+        )
+        assert conversion_account_name(lead) == "Lead abc"