diff --git a/src/pretix/base/invoice.py b/src/pretix/base/invoice.py
index c19641ef05..f1283ff8cb 100644
--- a/src/pretix/base/invoice.py
+++ b/src/pretix/base/invoice.py
@@ -389,6 +389,10 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
                 logger.exception("Can not resize image")
                 pass
             try:
+                # Valid ZUGFeRD invoices must be compliant with PDF/A-3. pretix-zugferd ensures this by passing them
+                # through ghost script. Unfortunately, if the logo contains transparency, this will still fail.
+                # I was unable to figure out a way to fix this in GhostScript, so the easy fix is to remove the
+                # transparency, as our invoices always have a white background anyways.
                 ir.remove_transparency()
             except:
                 logger.exception("Can not remove transparency from logo")