diff --git a/openapi/paths/invoices.yaml b/openapi/paths/invoices.yaml
index 7fc0c5373d..6215682601 100644
--- a/openapi/paths/invoices.yaml
+++ b/openapi/paths/invoices.yaml
@@ -701,24 +701,24 @@
               type: object
               properties:
                 email_type:
-                  type: enum
-                  description: "The email type to be sent, when bulk emailing invoices"
-                  enum:
-                    - invoice
-                    - quote
-                    - credit
-                    - payment
-                    - payment_partial
-                    - statement
-                    - reminder1
-                    - reminder2
-                    - reminder3
-                    - reminder_endless
-                    - custom1
-                    - custom2
-                    - custom3
-                    - purchase_order
-                    - email_quote_template_reminder1
+                  type: string
+                  description: |
+                    The email type to be sent, when bulk emailing invoices options include:
+                    - `invoice` (default)
+                    - `quote`
+                    - `credit`
+                    - `payment`
+                    - `payment_partial`
+                    - `statement`
+                    - `reminder1`
+                    - `reminder2`
+                    - `reminder3`
+                    - `reminder_endless`
+                    - `custom1`
+                    - `custom2`
+                    - `custom3`
+                    - `purchase_order`
+                    - `email_quote_template_reminder1`
                 action:
                   type: string
                   description: |