diff --git a/bin/History.txt b/bin/History.txt
index fdf84d96..d4dbe89b 100644
--- a/bin/History.txt
+++ b/bin/History.txt
@@ -10,7 +10,7 @@ Tom Charlesworth
 
 1.28.8.0 - 28 Jun 2019
 ----------------------
-. [Change #648] Support 50Hz(PAL) video refresh rate and implicitly PAL 1.018MHz.
+. [Change #648] Support 50Hz(PAL) video refresh rate and implicitly PAL 1.016MHz.
 	- NB. TV video modes still use NTSC rendering.
 . [Bug #656] Fix for PAGE1/2 ($C054/55) not having a 1 cycle delay.
 
diff --git a/source/Common.h b/source/Common.h
index 6cab9950..05662a8a 100644
--- a/source/Common.h
+++ b/source/Common.h
@@ -2,8 +2,8 @@
 
 const double _14M_NTSC = (157500000.0 / 11.0);	// 14.3181818... * 10^6
 const double _14M_PAL = 14.25045e6;				// UTAIIe:3-17
-const double CLK_6502_NTSC = ((_14M_NTSC * 65.0) / 912.0); // 65 cycles per 912 14M clocks
-const double CLK_6502_PAL = _14M_PAL / 14.0;
+const double CLK_6502_NTSC = (_14M_NTSC * 65.0) / (65.0*14.0+2.0); // 65 cycles per 912 14M clocks
+const double CLK_6502_PAL  = (_14M_PAL  * 65.0) / (65.0*14.0+2.0);
 //const double CLK_6502 = 23 * 44100;			// 1014300
 
 #define NUM_SLOTS 8