diff --git a/vars.mk b/vars.mk
index b9c3c602c01..54506dc514d 100644
--- a/vars.mk
+++ b/vars.mk
@@ -8,7 +8,7 @@ TOPDIR	?= ..
 INSTALL_STRIPPED ?= -s
 
 LDFLAGS += -L$(TOPDIR)/lib -L$(PREFIX)/lib -lxbps
-CPPFLAGS += -I$(TOPDIR)/include -D_XOPEN_SOURCE=600
+CPPFLAGS += -I$(TOPDIR)/include -D_BSD_SOURCE -D_XOPEN_SOURCE=600
 WARNFLAGS ?= -pedantic -std=c99 -Wall -Wextra -Werror -Wshadow -Wformat=2
 WARNFLAGS += -Wmissing-declarations -Wcomment -Wunused-macros -Wendif-labels
 CFLAGS += $(WARNFLAGS) -O2 -fPIC -DPIC