diff --git a/gnucash/report/business-reports/invoice.scm b/gnucash/report/business-reports/invoice.scm
index 7b99e1d08b..b5c9e3f32b 100644
--- a/gnucash/report/business-reports/invoice.scm
+++ b/gnucash/report/business-reports/invoice.scm
@@ -105,7 +105,7 @@
           (_ "Total"))))
 
 (define (monetary-or-percent numeric currency entry-type)
-  (if (gnc:entry-type-percent-p entry-type)
+  (if (eqv? entry-type GNC-AMT-TYPE-PERCENT)
       (string-append (gnc:default-html-gnc-numeric-renderer numeric #f) " " (_ "%"))
       (gnc:make-gnc-monetary currency numeric)))
 
diff --git a/libgnucash/engine/business-core.scm b/libgnucash/engine/business-core.scm
index 80e9737f98..f20d39044e 100644
--- a/libgnucash/engine/business-core.scm
+++ b/libgnucash/engine/business-core.scm
@@ -94,6 +94,8 @@
       (else ""))))
 
 (define (gnc:entry-type-percent-p type-val)
+  (issue-deprecation-warning
+   "gnc:entry-type-percent-p is deprecated.")
   (let ((type type-val))
     (equal? type GNC-AMT-TYPE-PERCENT)))