diff --git a/gtk2_ardour/lineset.cc b/gtk2_ardour/lineset.cc
index 61e5804ed4..352d9331eb 100644
--- a/gtk2_ardour/lineset.cc
+++ b/gtk2_ardour/lineset.cc
@@ -269,7 +269,7 @@ LineSet::line_at(double coord)
 	if (cached_pos != lines.end()) {
 		if (coord < cached_pos->coord) {
 			/* backward search */
-			while(--cached_pos != lines.end()) {
+			while (--cached_pos != lines.end()) {
 				if (cached_pos->coord <= coord) {
 					if (cached_pos->coord + cached_pos->width < coord) {
 						/* coord is between two lines */
@@ -281,7 +281,7 @@ LineSet::line_at(double coord)
 			}
 		} else {
 			/* forward search */
-			while(cached_pos != lines.end()) {
+			while (cached_pos != lines.end()) {
 				if (cached_pos->coord > coord) {
 					/* we searched past the line that we want, so now see
 					   if the previous line includes the coordinate */
diff --git a/gtk2_ardour/tempo_lines.cc b/gtk2_ardour/tempo_lines.cc
index 5b73c877ac..3d2f54a2ff 100644
--- a/gtk2_ardour/tempo_lines.cc
+++ b/gtk2_ardour/tempo_lines.cc
@@ -24,7 +24,7 @@
 
 using namespace std;
 
-#define MAX_CACHED_LINES 512
+#define MAX_CACHED_LINES 128
 	
 TempoLines::TempoLines(ArdourCanvas::Canvas& canvas, ArdourCanvas::Group* group)
 	: _canvas(canvas)
@@ -40,7 +40,7 @@ TempoLines::tempo_map_changed()
 	_clean_left = DBL_MAX;
 	_clean_right = 0.0;
 
-	size_t d = 0;
+	size_t d = 1;
 	// TODO: Dirty/slow, but 'needed' for zoom :(
 	for (Lines::iterator i = _lines.begin(); i != _lines.end(); ++d) {
 		Lines::iterator next = i;
@@ -98,6 +98,7 @@ TempoLines::draw (ARDOUR::TempoMap::BBTPointList& points, double frames_per_unit
 
 	if (beat_density > 4.0f) {
 		/* if the lines are too close together, they become useless */
+		tempo_map_changed();
 		return;
 	}
 
diff --git a/libs/evoral/evoral/TypeMap.hpp b/libs/evoral/evoral/TypeMap.hpp
index 3d082fc4ef..3ab8066f70 100644
--- a/libs/evoral/evoral/TypeMap.hpp
+++ b/libs/evoral/evoral/TypeMap.hpp
@@ -30,6 +30,8 @@ class Parameter;
  */
 class TypeMap {
 public:
+	virtual ~TypeMap() {}
+
 	/** Return true iff the type is a MIDI event.
 	 * The contents of the event will be used for specific ID
 	 */