diff --git a/Machines/Sinclair/ZXSpectrum/Video.hpp b/Machines/Sinclair/ZXSpectrum/Video.hpp
index 8419b882c..2c03545ec 100644
--- a/Machines/Sinclair/ZXSpectrum/Video.hpp
+++ b/Machines/Sinclair/ZXSpectrum/Video.hpp
@@ -88,9 +88,12 @@ template <VideoTiming timing> class Video {
 				.cycles_per_line = 228 * 2,
 				.lines_per_frame = 311,
 
-				.interrupt_time = 56545 * 2,
+				.interrupt_time = 56542 * 2,
 
-				.contention_leadin = 2 * 2,		// TODO: is this 2? Or 4? Or... ?
+				// i.e. video fetching begins five cycles after the start of the
+				// contended memory pattern below; that should put a clear two
+				// cycles between a Z80 access and the first video fetch.
+				.contention_leadin = 5 * 2,
 				.contention_duration = 129 * 2,
 
 				.delays = {
@@ -311,7 +314,9 @@ template <VideoTiming timing> class Video {
 			}
 
 			const int time_into_line = delay_time % timings.cycles_per_line;
-			if(time_into_line >= timings.contention_duration) return 0;
+			if(time_into_line >= timings.contention_duration) {
+				return 0;
+			}
 
 			return timings.delays[time_into_line & 15];
 		}