diff --git a/src/timescale.c b/src/timescale.c
index fa6ddc23..9ffb25f1 100644
--- a/src/timescale.c
+++ b/src/timescale.c
@@ -253,7 +253,7 @@ double novas_get_time(const novas_timespec *time, enum novas_timescale timescale
  * @param[out] ijd    [day] The integer part of the Julian date in the requested timescale. It may
  *                    be NULL if not required.
  * @return            [day] The fractional part of the Julian date in the requested timescale or
- *                    NAN is the time argument is NULL.
+ *                    NAN is the time argument is NULL (ijd will be set to -1 also).
  *
  * @sa novas_set_split_time()
  * @sa novas_get_time()
@@ -265,6 +265,8 @@ double novas_get_split_time(const novas_timespec *time, enum novas_timescale tim
   static const char *fn = "novas_get_split_time";
   double f;
 
+  if(ijd) *ijd = -1;
+
   if(!time) {
     novas_error(-1, EINVAL, fn, "NULL input time specification");
     return NAN;
@@ -443,7 +445,7 @@ int novas_set_unix_time(time_t unix_time, long nanos, int leap, double dut1, nov
  *
  * @param time        Pointer to the astronomical time specification data structure.
  * @param[out] nanos  [ns] UTC sub-second component. It may be NULL if not required.
- * @return            [s] The integer UNIX time
+ * @return            [s] The integer UNIX time, or -1 if the input time is NULL.
  *
  * @sa novas_set_unix_time()
  * @sa novas_get_time()
@@ -457,8 +459,11 @@ time_t novas_get_unix_time(const novas_timespec *time, long *nanos) {
   time_t seconds;
 
   sod = novas_get_split_time(time, NOVAS_UTC, &ijd) * DAY;
-  if(isnan(sod))
-    return novas_trace_nan("novas_get_unix_time");
+  if(isnan(sod)) {
+    static const char *fn = "novas_get_unix_time";
+    if(nanos) *nanos = novas_trace_nan(fn);
+    return novas_trace(fn, -1, 0);
+  }
 
   isod = (long) floor(sod);
   seconds = UNIX_J2000 + (ijd - IJD_J2000) * IDAY + isod;
diff --git a/test/src/test-errors.c b/test/src/test-errors.c
index 20d87c06..43d03d6f 100644
--- a/test/src/test-errors.c
+++ b/test/src/test-errors.c
@@ -1025,6 +1025,9 @@ static int test_time() {
   if(check_nan("time:get:scale:-1", novas_get_time(&time, -1))) n++;
   if(check_nan("time:get:scale:hi", novas_get_time(&time, NOVAS_TIMESCALES))) n++;
 
+  if(check("time:get_unix_time:time", -1, novas_offset_time(NULL, 0.1, &time))) n++;
+  if(check("time:get_unix_time:time+ijd", -1, novas_offset_time(NULL, 0.1, NULL))) n++;
+
   if(check("time:offset:time", -1, novas_offset_time(NULL, 0.1, &time))) n++;
   if(check("time:offset:out", -1, novas_offset_time(&time, 0.1, NULL))) n++;
   if(check("time:offset:both", -1, novas_offset_time(NULL, 0.1, NULL))) n++;
@@ -1033,6 +1036,15 @@ static int test_time() {
   if(check_nan("time:diff:t2", novas_diff_time(&time, NULL))) n++;
   if(check_nan("time:diff:both", novas_diff_time(NULL, NULL))) n++;
 
+  if(check_nan("time:diff_tcg:t1", novas_diff_tcg(NULL, &time))) n++;
+  if(check_nan("time:diff_tcg:t2", novas_diff_tcg(&time, NULL))) n++;
+  if(check_nan("time:diff_tcg:both", novas_diff_tcg(NULL, NULL))) n++;
+
+  if(check_nan("time:diff_tcb:t1", novas_diff_tcb(NULL, &time))) n++;
+  if(check_nan("time:diff_tcb:t2", novas_diff_tcb(&time, NULL))) n++;
+  if(check_nan("time:diff_tcb:both", novas_diff_tcb(NULL, NULL))) n++;
+
+
   return n;
 }