diff --git a/libsrc/nes/clock.s b/libsrc/nes/clock.s
index b36735e85..825283c9d 100644
--- a/libsrc/nes/clock.s
+++ b/libsrc/nes/clock.s
@@ -1,6 +1,11 @@
 ;
+; clock.s
+;
 ; Written by Groepaz/Hitmen <groepaz@gmx.net>
 ; Cleanup by Ullrich von Bassewitz <uz@cc65.org>
+; 2003-05-02, Greg King <gngking@erols.com>
+;
+; #include <time.h>
 ;
 ; clock_t clock (void);
 ;
@@ -16,8 +21,10 @@
         ldy    	#0  	    	; High word is always zero
        	sty     sreg+1
        	sty     sreg
-        ldx     tickcount+1    ; ## Problem: Cannot disable ints here
+L1:     ldx     tickcount+1
         lda     tickcount
+        cpx     tickcount+1     ; Did tickcount change?
+        bne     L1              ; Yes, re-read it
        	rts
 
 .endproc