diff --git a/ext/f2c_libs/Makefile.in b/ext/f2c_libs/Makefile.in
index 89909f078..bedf0aa29 100755
--- a/ext/f2c_libs/Makefile.in
+++ b/ext/f2c_libs/Makefile.in
@@ -187,10 +187,10 @@ xwsne.o:	lio.h
 xwsne.o:	fmt.h
 
 arith.h: arithchk.c
-	$(CC) $(CFLAGS) -DNO_FPINIT arithchk.c -lm ||\
-	 $(CC) -DNO_LONG_LONG $(CFLAGS) -DNO_FPINIT arithchk.c -lm
-	./a.out >arith.h
-	rm -f a.out arithchk.o
+	$(CC) $(CFLAGS) -o chkll -DNO_FPINIT arithchk.c -lm ||\
+	 $(CC) -DNO_LONG_LONG $(CFLAGS) -o chkll -DNO_FPINIT arithchk.c -lm
+	./chkll >arith.h
+	rm -f chkll* arithchk.o
 
 # depends target -> already in the Makefile
 depends: