diff --git a/sys/amd64/include/clock.h b/sys/amd64/include/clock.h
index 95888ce2384..b50ed659e62 100644
--- a/sys/amd64/include/clock.h
+++ b/sys/amd64/include/clock.h
@@ -19,6 +19,7 @@ extern u_int	i8254_freq;
 extern int	i8254_max_count;
 extern uint64_t	tsc_freq;
 extern int	tsc_is_invariant;
+extern int	tsc_perf_stat;
 
 void	i8254_init(void);
 
diff --git a/sys/i386/include/clock.h b/sys/i386/include/clock.h
index a351462e28b..75817d0c56b 100644
--- a/sys/i386/include/clock.h
+++ b/sys/i386/include/clock.h
@@ -19,6 +19,7 @@ extern u_int	i8254_freq;
 extern int	i8254_max_count;
 extern uint64_t	tsc_freq;
 extern int	tsc_is_invariant;
+extern int	tsc_perf_stat;
 
 void	i8254_init(void);