diff --git a/gtk2_ardour/editor_rulers.cc b/gtk2_ardour/editor_rulers.cc
index bdffd6fd39..a32353f9c4 100644
--- a/gtk2_ardour/editor_rulers.cc
+++ b/gtk2_ardour/editor_rulers.cc
@@ -1113,7 +1113,7 @@ Editor::compute_bbt_ruler_scale (framepos_t lower, framepos_t upper)
 
 	bbt_bars = _session->tempo_map().bbt_at_beat (ceil_upper_beat).bars - _session->tempo_map().bbt_at_beat (floor_lower_beat).bars;
 
-	beats = (ceil_upper_beat - floor_lower_beat) - bbt_bars;
+	beats = (ceil_upper_beat - floor_lower_beat);// - bbt_bars;  possible thinko; this fixes the problem (for me) where measure lines alternately appear&disappear while playing at certain zoom scales
 	double beat_density = ((beats + 1) * ((double) (upper - lower) / (double) (1 + beat_after_upper_pos - beat_before_lower_pos))) / 5.0;
 
 	/* Only show the bar helper if there aren't many bars on the screen */