diff --git a/core/classes/mixin/mixin.factor b/core/classes/mixin/mixin.factor
index ec5c2ef2e4..706651cacf 100644
--- a/core/classes/mixin/mixin.factor
+++ b/core/classes/mixin/mixin.factor
@@ -18,11 +18,11 @@ M: mixin-class reset-class
 
 M: mixin-class rank-class drop 8 ;
 
-TUPLE: check-mixin-class class ;
+ERROR: check-mixin-class-error class ;
 
 : check-mixin-class ( mixin -- mixin )
     dup mixin-class? [
-        \ check-mixin-class boa throw
+        check-mixin-class-error
     ] unless ;
 
 <PRIVATE
diff --git a/core/generic/generic.factor b/core/generic/generic.factor
index 3e3a135392..e81212bf18 100644
--- a/core/generic/generic.factor
+++ b/core/generic/generic.factor
@@ -89,11 +89,11 @@ ERROR: no-next-method method ;
 : (call-next-method) ( method -- )
     dup next-method-quot [ call ] [ no-next-method ] ?if ;
 
-TUPLE: check-method class generic ;
+ERROR: check-method-error class generic ;
 
 : check-method ( classoid generic -- class generic )
     2dup [ classoid? ] [ generic? ] bi* and [
-        \ check-method boa throw
+        check-method-error
     ] unless ; inline
 
 : remake-generic ( generic -- )