diff --git a/lab/vtsh/lib/exec.c b/lab/vtsh/lib/exec.c
index a8e6e24..fe588f8 100644
--- a/lab/vtsh/lib/exec.c
+++ b/lab/vtsh/lib/exec.c
@@ -139,7 +139,8 @@ static int run_one(const Cmd* c) {
   waitpid(pid, &st, 0);
   long long t1 = nsec_now();
 
-  fprintf(stderr, "time_ns=%lld\n", (t1 - t0));
+  double elapsed_ms = (double)(t1 - t0) / 1000000.0;
+  fprintf(stderr, "time_ms=%.3f\n", elapsed_ms);
 
   if (WIFEXITED(st))
     return WEXITSTATUS(st);