diff --git a/usr.sbin/pcvt/vgaio/Makefile b/usr.sbin/pcvt/vgaio/Makefile
index b9289f5254a9..ded8bdf9b3b9 100644
--- a/usr.sbin/pcvt/vgaio/Makefile
+++ b/usr.sbin/pcvt/vgaio/Makefile
@@ -22,6 +22,7 @@ YACC=	yacc
 LFLAGS+= -I
 LDADD=	-lm -ly -ll
 
+CFLAGS=	-O2	# due to a gcc bug, it compiles only with -O2!
 CFLAGS+= -I ${.CURDIR}/obj -I ${.CURDIR} -g
 
 CLEANFILES+= y.tab.h