diff --git a/src/ftracetool.c b/src/ftracetool.c
index d91bdfe..81e5a60 100644
--- a/src/ftracetool.c
+++ b/src/ftracetool.c
@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <unistd.h>
 
 #include <chibi/eval.h>
@@ -34,6 +35,7 @@ struct ftt_mapping
     struct ftt_mapping *next;
 };
 
+static double g_wait_sec = 0;
 static int g_max_lines = 0;
 
 static struct ftt_mapping *gs_mappings;
@@ -318,10 +320,14 @@ static sexp display_exception(sexp ctx, sexp self, sexp_sint_t n, sexp arg0)
 
 static sexp sexp_sleep_stub(sexp ctx, sexp self, sexp_sint_t n, sexp arg0)
 {
+    struct timespec ts;
     sexp res;
-    if (!sexp_numberp(arg0))
-        return sexp_type_exception(ctx, self, SEXP_NUMBER, arg0);
-    sleep(sexp_uint_value(arg0));
+    if (!sexp_flonump(arg0))
+        return sexp_type_exception(ctx, self, SEXP_FLONUM, arg0);
+    float sleep_sec = sexp_flonum_value(arg0);
+    ts.tv_sec = sleep_sec;
+    ts.tv_nsec = (sleep_sec - ts.tv_sec) * 1e9;
+    nanosleep(&ts, NULL);
     return res;
 }
 
@@ -579,7 +585,7 @@ static int register_sleep(sexp ctx)
     if (sexp_opcodep(op))
     {
         sexp_opcode_return_type(op) = sexp_make_fixnum(SEXP_NULL);
-        sexp_opcode_arg1_type(op) = sexp_make_fixnum(SEXP_NUMBER);
+        sexp_opcode_arg1_type(op) = sexp_make_fixnum(SEXP_FLONUM);
     }
     sexp_gc_release1(ctx);
 
@@ -719,7 +725,7 @@ int main(int argc, char **argv)
     char filename[NAME_MAX] = {};
     bool execute_script = false;
     bool show_symbols_in_file = false;
-    while ((opt = getopt(argc, argv, "vhs:e:m:")) != -1)
+    while ((opt = getopt(argc, argv, "vhs:e:m:l:")) != -1)
     {
         switch (opt)
         {
@@ -750,6 +756,16 @@ int main(int argc, char **argv)
             g_max_lines = atoi(optarg);
             break;
         }
+        case 'w':
+        {
+            char *end = NULL;
+            const double wait_sec = strtod(optarg, &end);
+            if (end != optarg)
+            {
+                g_wait_sec = wait_sec;
+            }
+            break;
+        }
         case 'm':
         {
             struct ftt_mapping *const mapping = parse_mapping(optarg);
diff --git a/src/ftracetool.scm b/src/ftracetool.scm
index b73e76e..85e17d1 100644
--- a/src/ftracetool.scm
+++ b/src/ftracetool.scm
@@ -65,7 +65,7 @@
   (case-lambda
    (()
     (display "Do waiting\n")
-    (sleep 1))
+    (sleep 1.0))
    ((probe . rest)
     (let ((token ((probe-install-handler probe))))
       (guard (x
@@ -238,6 +238,9 @@
         (display "0")
         (newline)))
     (let ((events (read-trace-events-from-file "/sys/kernel/tracing/trace" max-lines)))
+      (display "Processing entries: ")
+      (display (length events))
+      (newline)
       (for-each
        (lambda (event)
          (let ((probe (find-subprobe (trace-event-probe-id event) subprobes)))