diff --git a/Storage/Disk/Drive.cpp b/Storage/Disk/Drive.cpp
index afa5e4938..21d769a97 100644
--- a/Storage/Disk/Drive.cpp
+++ b/Storage/Disk/Drive.cpp
@@ -66,6 +66,7 @@ Storage::Time Drive::get_time_into_track() {
 	Time result(cycles_since_index_hole_, (int)get_input_clock_rate());
 	result /= rotational_multiplier_;
 	result.simplify();
+	assert(result <= Time(1));
 	return result;
 }
 
@@ -92,6 +93,7 @@ void Drive::set_event_delegate(Storage::Disk::Drive::EventDelegate *delegate) {
 }
 
 void Drive::advance(const Cycles cycles) {
+	cycles_since_index_hole_ += (unsigned int)cycles.as_int();
 	if(event_delegate_) event_delegate_->advance(cycles);
 }
 
@@ -99,9 +101,6 @@ void Drive::run_for(const Cycles cycles) {
 	Time zero(0);
 
 	if(has_disk_ && motor_is_on_) {
-		// Grab a new track if not already in possession of one.
-		if(!track_) setup_track();
-
 		int number_of_cycles = cycles.as_int();
 		while(number_of_cycles) {
 			int cycles_until_next_event = (int)get_cycles_until_next_event();
@@ -112,8 +111,6 @@ void Drive::run_for(const Cycles cycles) {
 				cycles_to_run_for = std::min(cycles_to_run_for, write_cycles_target);
 			}
 
-			cycles_since_index_hole_ += (unsigned int)cycles_to_run_for;
-
 			number_of_cycles -= cycles_to_run_for;
 			if(!is_reading_) {
 				if(cycles_until_bits_written_ > zero) {
@@ -137,6 +134,13 @@ void Drive::run_for(const Cycles cycles) {
 #pragma mark - Track timed event loop
 
 void Drive::get_next_event(const Time &duration_already_passed) {
+	// Grab a new track if not already in possession of one. This will recursively call get_next_event,
+	// supplying a proper duration_already_passed.
+	if(!track_) {
+		setup_track();
+		return;
+	}
+
 	if(track_) {
 		current_event_ = track_->get_next_event();
 	} else {
@@ -154,7 +158,10 @@ void Drive::get_next_event(const Time &duration_already_passed) {
 
 void Drive::process_next_event() {
 	// TODO: ready test here.
-	if(current_event_.type == Track::Event::IndexHole) cycles_since_index_hole_ = 0;
+	if(current_event_.type == Track::Event::IndexHole) {
+		assert(get_time_into_track() == Time(1) || get_time_into_track() == Time(0));
+		cycles_since_index_hole_ = 0;
+	}
 	if(event_delegate_) event_delegate_->process_event(current_event_);
 	get_next_event(Time(0));
 }
@@ -181,9 +188,9 @@ void Drive::setup_track() {
 	assert(track_time_now >= Time(0) && current_event_.length <= Time(1));
 
 	Time time_found = track_->seek_to(track_time_now);
-	assert(time_found >= Time(0) && time_found <= track_time_now);
-	offset = track_time_now - time_found;
+	assert(time_found >= Time(0) && time_found < Time(1) && time_found <= track_time_now);
 
+	offset = track_time_now - time_found;
 	get_next_event(offset);
 }
 
diff --git a/Storage/TimedEventLoop.cpp b/Storage/TimedEventLoop.cpp
index 6b1b1a597..ad54c1051 100644
--- a/Storage/TimedEventLoop.cpp
+++ b/Storage/TimedEventLoop.cpp
@@ -8,7 +8,9 @@
 
 #include "TimedEventLoop.hpp"
 #include "../NumberTheory/Factors.hpp"
+
 #include <algorithm>
+#include <cassert>
 
 using namespace Storage;
 
@@ -17,8 +19,14 @@ TimedEventLoop::TimedEventLoop(unsigned int input_clock_rate) :
 
 void TimedEventLoop::run_for(const Cycles cycles) {
 	int remaining_cycles = cycles.as_int();
+#ifndef NDEBUG
+	int cycles_advanced = 0;
+#endif
 
 	while(cycles_until_event_ <= remaining_cycles) {
+#ifndef NDEBUG
+		cycles_advanced += cycles_until_event_;
+#endif
 		advance(cycles_until_event_);
 		remaining_cycles -= cycles_until_event_;
 		cycles_until_event_ = 0;
@@ -27,8 +35,14 @@ void TimedEventLoop::run_for(const Cycles cycles) {
 
 	if(remaining_cycles) {
 		cycles_until_event_ -= remaining_cycles;
+#ifndef NDEBUG
+		cycles_advanced += remaining_cycles;
+#endif
 		advance(remaining_cycles);
 	}
+
+	assert(cycles_advanced == cycles.as_int());
+	assert(cycles_until_event_ > 0);
 }
 
 unsigned int TimedEventLoop::get_cycles_until_next_event() {
@@ -65,7 +79,9 @@ void TimedEventLoop::set_next_event_time_interval(Time interval) {
 
 	// So this event will fire in the integral number of cycles from now, putting us at the remainder
 	// number of subcycles
+	assert(cycles_until_event_ == 0);
 	cycles_until_event_ += (int)(numerator / denominator);
+	assert(cycles_until_event_ >= 0);
 	subcycles_until_event_.length = (unsigned int)(numerator % denominator);
 	subcycles_until_event_.clock_rate = (unsigned int)denominator;
 }