diff --git a/src/drivers/ins/vectornav/libvnc/include/vn/util.h b/src/drivers/ins/vectornav/libvnc/include/vn/util.h
index 02388f41f0..6da16dfd1c 100644
--- a/src/drivers/ins/vectornav/libvnc/include/vn/util.h
+++ b/src/drivers/ins/vectornav/libvnc/include/vn/util.h
@@ -11,6 +11,10 @@
 #include "vn/util/export.h"
 #include "vn/types.h"
 
+#ifndef UNUSED
+#define UNUSED(x) (void)(sizeof(x))
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/drivers/ins/vectornav/libvnc/src/vn/protocol/spi.c b/src/drivers/ins/vectornav/libvnc/src/vn/protocol/spi.c
index d162a2f9aa..fefce9ba51 100644
--- a/src/drivers/ins/vectornav/libvnc/src/vn/protocol/spi.c
+++ b/src/drivers/ins/vectornav/libvnc/src/vn/protocol/spi.c
@@ -2,8 +2,6 @@
 #include <string.h>
 #include "vn/util.h"
 
-//#define UNUSED(x) (void)(sizeof(x))
-
 VnError VnSpi_genGenericCommand(
 	char cmdId,
 	char* buffer,
diff --git a/src/drivers/ins/vectornav/libvnc/src/vn/xplat/event.c b/src/drivers/ins/vectornav/libvnc/src/vn/xplat/event.c
index 958315b042..996fa4cd1b 100644
--- a/src/drivers/ins/vectornav/libvnc/src/vn/xplat/event.c
+++ b/src/drivers/ins/vectornav/libvnc/src/vn/xplat/event.c
@@ -1,7 +1,9 @@
 /* Enable IEEE Std 1003.1b-1993 functionality required for clock_gettime. */
 #if defined(__linux__) || defined(__NUTTX__)
 	/* Works for Ubuntu 15.10 */
+#ifndef _POSIX_C_SOURCE
 	#define _POSIX_C_SOURCE 199309L
+#endif
 #elif defined __CYGWIN__
 	/* Works for Cygwin 2.4.0 64-bit */
 	#define _POSIX_TIMERS 	1
diff --git a/src/drivers/ins/vectornav/libvnc/src/vn/xplat/time.c b/src/drivers/ins/vectornav/libvnc/src/vn/xplat/time.c
index f06d415de0..9548f8c653 100644
--- a/src/drivers/ins/vectornav/libvnc/src/vn/xplat/time.c
+++ b/src/drivers/ins/vectornav/libvnc/src/vn/xplat/time.c
@@ -1,7 +1,9 @@
 /* Enable IEEE Std 1003.1b-1993 functionality required for clock_gettime. */
 #if defined(__linux__) || defined(__NUTTX__)
 	/* Works for Ubuntu 15.10 */
+#ifndef _POSIX_C_SOURCE
 	#define _POSIX_C_SOURCE 199309L
+#endif
 #elif defined __CYGWIN__
 	/* Works for Cygwin 2.4.0 64-bit */
 	#define _POSIX_TIMERS 				1