diff --git a/makefile b/makefile
index fe0dcbd..fd032f5 100644
--- a/makefile
+++ b/makefile
@@ -17,10 +17,15 @@
 
 KBUILD_OUTPUT ?= /lib/modules/$(shell uname -r)/build
 
+FEAT_CFLAGS :=
+ifneq ($(shell grep clock_adjtime /usr/include/bits/time.h),)
+FEAT_CFLAGS += -D_GNU_SOURCE -DHAVE_CLOCK_ADJTIME
+endif
+
 DEBUG	=
 CC	= $(CROSS_COMPILE)gcc
 INC	= -I$(KBUILD_OUTPUT)/usr/include
-CFLAGS	= -Wall $(INC) $(DEBUG) $(EXTRA_CFLAGS)
+CFLAGS	= -Wall $(INC) $(DEBUG) $(FEAT_CFLAGS) $(EXTRA_CFLAGS)
 LDLIBS	= -lm -lrt $(EXTRA_LDFLAGS)
 PRG	= ptp4l pmc phc2sys hwstamp_ctl
 OBJ	= bmc.o clock.o config.o fsm.o ptp4l.o mave.o msg.o phc.o pi.o port.o \
diff --git a/missing.h b/missing.h
index bf82df5..fbd57d4 100644
--- a/missing.h
+++ b/missing.h
@@ -44,10 +44,12 @@
 #define FD_TO_CLOCKID(fd)	((~(clockid_t) (fd) << 3) | CLOCKFD)
 #define CLOCKID_TO_FD(clk)	((unsigned int) ~((clk) >> 3))
 
+#ifndef HAVE_CLOCK_ADJTIME
 static inline int clock_adjtime(clockid_t id, struct timex *tx)
 {
 	return syscall(__NR_clock_adjtime, id, tx);
 }
+#endif
 
 #ifndef __uClinux__