diff --git a/lib/plausible/billing/billing.ex b/lib/plausible/billing/billing.ex
index 63bbf647a..cea0b107f 100644
--- a/lib/plausible/billing/billing.ex
+++ b/lib/plausible/billing/billing.ex
@@ -8,7 +8,7 @@ defmodule Plausible.Billing do
   end
 
   def subscription_created(params) do
-    params = if params["passthrough"] do
+    params = if present?(params["passthrough"]) do
       params
     else
       user = Repo.get_by(Plausible.Auth.User, email: params["email"])
@@ -137,4 +137,9 @@ defmodule Plausible.Billing do
       next_bill_amount: params["unit_price"] || params["new_unit_price"]
     }
   end
+
+  defp present?(""), do: false
+  defp present?(nil), do: false
+  defp present?(_), do: true
+
 end
diff --git a/test/plausible/billing/billing_test.exs b/test/plausible/billing/billing_test.exs
index 835de38cf..4452c9dcf 100644
--- a/test/plausible/billing/billing_test.exs
+++ b/test/plausible/billing/billing_test.exs
@@ -45,6 +45,7 @@ defmodule Plausible.BillingTest do
       user = insert(:user)
 
       Billing.subscription_created(%{
+        "passthrough" => "",
         "email" => user.email,
         "alert_name" => "subscription_created",
         "subscription_id" => @subscription_id,