diff --git a/classes/dm-verity-img.bbclass b/classes/dm-verity-img.bbclass
index 48557e9..73297ca 100644
--- a/classes/dm-verity-img.bbclass
+++ b/classes/dm-verity-img.bbclass
@@ -187,6 +187,10 @@ def get_verity_fstypes(d):
     verity_hash = d.getVar('DM_VERITY_SEPARATE_HASH')
     pn = d.getVar('PN')
 
+    if not verity_image or not verity_type:
+        bb.warnonce('dm-verity-img class inherited in %s but not used' % pn)
+        return ""
+
     fstypes = ""
     if not pn.endswith(verity_image):
         return fstypes # This doesn't concern this image
@@ -207,7 +211,6 @@ python __anonymous() {
     pn = d.getVar('PN')
 
     if not verity_image or not verity_type:
-        bb.warn('dm-verity-img class inherited but not used')
         return
 
     if not pn.endswith(verity_image):