diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index 86bbb62137b7..07b4a9d7b7bd 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -24,7 +24,7 @@ COPTFLAGS?=-O2 -frename-registers -pipe
 . elif ${MACHINE_ARCH} == "ia64"
 COPTFLAGS?=-O2 -pipe
 . elif ${MACHINE_ARCH} == "sparc64"
-COPTFLAGS?=-O -pipe
+COPTFLAGS?=-O2 -pipe
 . elif ${MACHINE_ARCH} == "arm"
 COPTFLAGS?=-O2 -pipe
 . else