diff --git a/src/xrt/auxiliary/os/os_time.h b/src/xrt/auxiliary/os/os_time.h
index 3212c26e0..a141814ae 100644
--- a/src/xrt/auxiliary/os/os_time.h
+++ b/src/xrt/auxiliary/os/os_time.h
@@ -75,7 +75,7 @@ extern "C" {
  * Return a monotonic clock in nanoseconds.
  * @ingroup aux_os_time
  */
-static inline uint64_t
+static inline int64_t
 os_monotonic_get_ns(void);
 
 /*!
@@ -133,7 +133,7 @@ os_precise_sleeper_nanosleep(struct os_precise_sleeper *ops, int32_t nsec);
  *
  * @ingroup aux_os_time_extra
  */
-static inline uint64_t
+static inline int64_t
 os_timespec_to_ns(const struct timespec *spec);
 
 /*!
@@ -143,7 +143,7 @@ os_timespec_to_ns(const struct timespec *spec);
  * @ingroup aux_os_time_extra
  */
 static inline void
-os_ns_to_timespec(uint64_t ns, struct timespec *spec);
+os_ns_to_timespec(int64_t ns, struct timespec *spec);
 #endif
 
 #if defined(XRT_HAVE_TIMEVAL) || defined(XRT_DOXYGEN)
@@ -151,7 +151,7 @@ os_ns_to_timespec(uint64_t ns, struct timespec *spec);
  * Convert a timeval struct to nanoseconds.
  * @ingroup aux_os_time_extra
  */
-static inline uint64_t
+static inline int64_t
 os_timeval_to_ns(struct timeval *val);
 #endif
 
@@ -161,7 +161,7 @@ os_timeval_to_ns(struct timeval *val);
  *
  * @ingroup aux_os_time_extra
  */
-static inline uint64_t
+static inline int64_t
 os_realtime_get_ns(void);
 #endif
 
@@ -171,7 +171,7 @@ os_realtime_get_ns(void);
  *
  * @ingroup aux_os_time_extra
  */
-uint64_t
+int64_t
 os_realtime_get_ns(void);
 #endif
 
@@ -258,17 +258,17 @@ os_precise_sleeper_nanosleep(struct os_precise_sleeper *ops, int32_t nsec)
 }
 
 #if defined(XRT_HAVE_TIMESPEC)
-static inline uint64_t
+static inline int64_t
 os_timespec_to_ns(const struct timespec *spec)
 {
-	uint64_t ns = 0;
-	ns += (uint64_t)spec->tv_sec * U_1_000_000_000;
-	ns += (uint64_t)spec->tv_nsec;
+	int64_t ns = 0;
+	ns += (int64_t)spec->tv_sec * U_1_000_000_000;
+	ns += (int64_t)spec->tv_nsec;
 	return ns;
 }
 
 static inline void
-os_ns_to_timespec(uint64_t ns, struct timespec *spec)
+os_ns_to_timespec(int64_t ns, struct timespec *spec)
 {
 	spec->tv_sec = (ns / U_1_000_000_000);
 	spec->tv_nsec = (ns % U_1_000_000_000);
@@ -280,12 +280,12 @@ os_ns_to_timespec(uint64_t ns, struct timespec *spec)
 
 #define OS_NS_PER_USEC (1000)
 
-static inline uint64_t
+static inline int64_t
 os_timeval_to_ns(struct timeval *val)
 {
-	uint64_t ns = 0;
-	ns += (uint64_t)val->tv_sec * U_1_000_000_000;
-	ns += (uint64_t)val->tv_usec * OS_NS_PER_USEC;
+	int64_t ns = 0;
+	ns += (int64_t)val->tv_sec * U_1_000_000_000;
+	ns += (int64_t)val->tv_usec * OS_NS_PER_USEC;
 	return ns;
 }
 #endif // defined(XRT_HAVE_TIMEVAL) && defined(XRT_OS_LINUX)
@@ -305,7 +305,7 @@ os_ns_per_qpc_tick_get(void)
 }
 #endif // defined(XRT_OS_WINDOWS)
 
-static inline uint64_t
+static inline int64_t
 os_monotonic_get_ns(void)
 {
 #if defined(XRT_OS_LINUX)
@@ -326,7 +326,7 @@ os_monotonic_get_ns(void)
 }
 
 #ifdef XRT_OS_LINUX
-static inline uint64_t
+static inline int64_t
 os_realtime_get_ns(void)
 {
 	struct timespec ts;
diff --git a/src/xrt/drivers/vive/vive_device.c b/src/xrt/drivers/vive/vive_device.c
index d76fc9399..252bc34fc 100644
--- a/src/xrt/drivers/vive/vive_device.c
+++ b/src/xrt/drivers/vive/vive_device.c
@@ -882,8 +882,8 @@ vive_sensors_run_thread(void *ptr)
 	 * read packets with a noop function for 50ms.
 	 */
 
-	uint64_t then_ns = os_monotonic_get_ns();
-	uint64_t future_50ms_ns = then_ns + U_TIME_1MS_IN_NS * (uint64_t)50;
+	int64_t then_ns = os_monotonic_get_ns();
+	int64_t future_50ms_ns = then_ns + U_TIME_1MS_IN_NS * (int64_t)50;
 
 	while (future_50ms_ns > os_monotonic_get_ns() && os_thread_helper_is_running(&d->sensors_thread)) {
 		// Lock not held.
diff --git a/src/xrt/drivers/wmr/wmr_controller_base.c b/src/xrt/drivers/wmr/wmr_controller_base.c
index 1d46114fd..dd627e74c 100644
--- a/src/xrt/drivers/wmr/wmr_controller_base.c
+++ b/src/xrt/drivers/wmr/wmr_controller_base.c
@@ -125,8 +125,8 @@ wmr_controller_send_fw_cmd(struct wmr_controller_base *wcb,
 	// comms timeout. Replies are usually in 10ms or so but the first can take longer
 	const int timeout_ms = 250;
 	const int timeout_ns = timeout_ms * U_TIME_1MS_IN_NS;
-	uint64_t timeout_start = os_monotonic_get_ns();
-	uint64_t timeout_end_ns = timeout_start + timeout_ns;
+	int64_t timeout_start = os_monotonic_get_ns();
+	int64_t timeout_end_ns = timeout_start + timeout_ns;
 
 	if (!wmr_controller_send_bytes(wcb, fw_cmd->buf, sizeof(fw_cmd->buf))) {
 		return -1;