-AT_CHECK([[bison -o glr-regr18.c glr-regr18.y]], 0, [],
-[glr-regr18.y:26.13-19: warning: result type clash on merge function `merge': <type2> != <type1>
-glr-regr18.y:25.18-24: warning: first declaration
+AT_BISON_CHECK([[-o glr-regr18.c glr-regr18.y]], 1, [],
+[glr-regr18.y:26.18-24: result type clash on merge function `merge': <type2> != <type1>
+glr-regr18.y:25.18-24: previous declaration
+glr-regr18.y:27.13-19: result type clash on merge function `merge': <type3> != <type2>
+glr-regr18.y:26.18-24: previous declaration