diff --git a/gtests/net/packetdrill/Makefile.SunOS b/gtests/net/packetdrill/Makefile.SunOS
index 428b95999b59f3a0908eebb65c11d3505ff0e50d..c7c40d94684d6448ba7886e58be4d9851c243d02 100644
--- a/gtests/net/packetdrill/Makefile.SunOS
+++ b/gtests/net/packetdrill/Makefile.SunOS
@@ -1,2 +1,3 @@
 packetdrill-ext-libs := -lsocket -lnsl -lsctp -lpcap
+CFLAGS += -D_XPG4_2 -D__EXTENSIONS__
 include Makefile.common