diff --git a/include/asm-x86/tsc.h b/include/asm-x86/tsc.h
index a4d8066..2002f8d 100644
--- a/include/asm-x86/tsc.h
+++ b/include/asm-x86/tsc.h
@@ -72,4 +72,8 @@
 extern void check_tsc_sync_source(int cpu);
 extern void check_tsc_sync_target(void);
 
+#ifdef CONFIG_X86_64
+extern void tsc_calibrate(void);
+#endif
+
 #endif