diff --git a/src/system/libroot/posix/time/clock_support.cpp b/src/system/libroot/posix/time/clock_support.cpp
index 6f214f8660..b7e44f3cca 100644
--- a/src/system/libroot/posix/time/clock_support.cpp
+++ b/src/system/libroot/posix/time/clock_support.cpp
@@ -14,6 +14,7 @@
 #include <OS.h>
 
 #include <errno_private.h>
+#include <time_private.h>
 #include <syscall_utils.h>
 
 #include <syscalls.h>
@@ -106,12 +107,10 @@ clock_nanosleep(clockid_t clockID, int flags, const struct timespec* time,
 	struct timespec* remainingTime)
 {
 	// convert time to microseconds (round up)
-	if (time->tv_sec < 0 || time->tv_nsec < 0 || time->tv_nsec >= 1000000000)
+	bigtime_t microSeconds;
+	if (!timespec_to_bigtime(*time, microSeconds))
 		RETURN_AND_TEST_CANCEL(EINVAL);
 
-	bigtime_t microSeconds = (bigtime_t)time->tv_sec * 1000000
-		+ (time->tv_nsec + 999) / 1000;
-
 	// get timeout flags
 	uint32 timeoutFlags;
 	if ((flags & TIMER_ABSTIME) != 0) {