diff -r 34b3366b83ac -r b6456ccd9e3e src/HOL/ex/IntRing.thy
--- a/src/HOL/ex/IntRing.thy	Thu Oct 01 18:29:53 1998 +0200
+++ b/src/HOL/ex/IntRing.thy	Thu Oct 01 18:30:05 1998 +0200
@@ -10,7 +10,7 @@
 IntRing = IntRingDefs + Lagrange +
 
 instance int :: add_semigroup (zadd_assoc)
-instance int :: add_monoid (zero_int_def,zadd_0,zadd_0_right)
+instance int :: add_monoid (zero_int_def,zadd_nat0,zadd_nat0_right)
 instance int :: add_group (left_inv_int,minus_inv_int)
 instance int :: add_agroup (zadd_commute)
 instance int :: ring (zmult_assoc,zadd_zmult_distrib2,zadd_zmult_distrib)