diff --git a/abduco.c b/abduco.c
index b878cc6..3b3733d 100644
--- a/abduco.c
+++ b/abduco.c
@@ -28,6 +28,7 @@
 #include <termios.h>
 #include <time.h>
 #include <unistd.h>
+#include <sys/select.h>
 #include <sys/stat.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
diff --git a/config.mk b/config.mk
index 9d93940..71930ad 100644
--- a/config.mk
+++ b/config.mk
@@ -15,7 +15,8 @@ LIBS = -lc -lutil
 # Solaris
 #LIBS = -lc -lsocket
 
-CFLAGS += -std=c99 -Os ${INCS} -DVERSION=\"${VERSION}\" -DNDEBUG -D_GNU_SOURCE
+CFLAGS += -std=c99 -Os ${INCS} -DVERSION=\"${VERSION}\" -DNDEBUG -D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700
+
 LDFLAGS += ${LIBS}
 
 DEBUG_CFLAGS = ${CFLAGS} -UNDEBUG -O0 -g -ggdb -Wall