diff --git a/source/system.h b/source/system.h
index 3bfb2ba..5de31d0 100644
--- a/source/system.h
+++ b/source/system.h
@@ -57,7 +57,7 @@ extern uint32 count_z80;
 extern uint16 misc68Kcycles;
 extern uint16 miscZ80cycles;
 extern uint16 lines_per_frame;
-extern double CPU_Clock;
+extern double Master_Clock;
 
 /* Function prototypes */
 void system_init (void);