diff --git a/sys/contrib/altq/altq/altq_hfsc.c b/sys/contrib/altq/altq/altq_hfsc.c
diff --git a/sys/contrib/altq/altq/altq_subr.c b/sys/contrib/altq/altq/altq_subr.c
index 7426e75..0c6e485 100644
--- a/sys/contrib/altq/altq/altq_subr.c
+++ b/sys/contrib/altq/altq/altq_subr.c
@@ -383,6 +383,7 @@ tbr_set(ifq, profile)
 	if (tbr_dequeue_ptr == NULL)
 		tbr_dequeue_ptr = tbr_dequeue;
 
+	tbr_callout_init();
 	if (machclk_freq == 0)
 		init_machclk();
 	if (machclk_freq == 0) {
@@ -917,13 +918,26 @@ EVENTHANDLER_DEFINE(cpufreq_post_change, tsc_freq_changed, NULL,
     EVENTHANDLER_PRI_ANY);
 #endif /* __FreeBSD_version >= 700035 */
 
+#if (__FreeBSD_version >= 600000)
+/*
+ * Initializes the callout. OBVIOUS: should be called before the
+ * first use of the tbr_callout.
+ */
 void
-init_machclk(void)
+tbr_callout_init(void)
 {
-#if (__FreeBSD_version >= 600000)
-	callout_init(&tbr_callout, 0);
-#endif
+	static int called = 0;
 
+	if (!called) {
+		callout_init(&tbr_callout, 0);
+		called = 1;
+	}
+}
+#endif /* __FreeBSD_version >= 600000 */
+
+void
+init_machclk(void)
+{
 	machclk_usepcc = 1;
 
 #if (!defined(__i386__) && !defined(__alpha__)) || defined(ALTQ_NOPCC)
diff --git a/sys/contrib/altq/altq/altq_var.h b/sys/contrib/altq/altq/altq_var.h
index 99407fb..3879a28 100644
--- a/sys/contrib/altq/altq/altq_var.h
+++ b/sys/contrib/altq/altq/altq_var.h
@@ -125,6 +125,11 @@ extern void init_machclk(void);
 extern u_int64_t read_machclk(void);
 
 /*
+ * Callout initializer.
+ */
+extern void tbr_callout_init(void);
+
+/*
  * debug support
  */
 #ifdef ALTQ_DEBUG