diff --git a/sys/schedstatistics/schedstatistics.c b/sys/schedstatistics/schedstatistics.c
index 0f5c78d0dd..92743ca6ba 100644
--- a/sys/schedstatistics/schedstatistics.c
+++ b/sys/schedstatistics/schedstatistics.c
@@ -31,15 +31,18 @@ void sched_statistics_cb(kernel_pid_t active_thread, kernel_pid_t next_thread)
 {
     uint32_t now = xtimer_now().ticks32;
 
-    /* Update active thread runtime, there is always an active thread since
-       first sched_run happens when main_trampoline gets scheduled */
-    schedstat_t *active_stat = &sched_pidlist[active_thread];
-    active_stat->runtime_ticks += now - active_stat->laststart;
+    /* Update active thread stats */
+    if (active_thread != KERNEL_PID_UNDEF) {
+        schedstat_t *active_stat = &sched_pidlist[active_thread];
+        active_stat->runtime_ticks += now - active_stat->laststart;
+    }
 
     /* Update next_thread stats */
-    schedstat_t *next_stat = &sched_pidlist[next_thread];
-    next_stat->laststart = now;
-    next_stat->schedules++;
+    if (next_thread != KERNEL_PID_UNDEF) {
+        schedstat_t *next_stat = &sched_pidlist[next_thread];
+        next_stat->laststart = now;
+        next_stat->schedules++;
+    }
 }
 
 void init_schedstatistics(void)