diff --git a/Components/9918/9918.cpp b/Components/9918/9918.cpp
index 11512c7ae..07ff15c8f 100644
--- a/Components/9918/9918.cpp
+++ b/Components/9918/9918.cpp
@@ -190,7 +190,9 @@ void TMS9918::run_for(const HalfCycles cycles) {
 	int read_cycles_pool = int_cycles;
 
 	while(write_cycles_pool || read_cycles_pool) {
+#ifndef NDEBUG
 		LineBufferPointer backup = read_pointer_;
+#endif
 
 		if(write_cycles_pool) {
 			// Determine how much writing to do.
@@ -329,8 +331,10 @@ void TMS9918::run_for(const HalfCycles cycles) {
 		}
 
 
+#ifndef NDEBUG
 		assert(backup.row == read_pointer_.row && backup.column == read_pointer_.column);
 		backup = write_pointer_;
+#endif
 
 
 		if(read_cycles_pool) {
diff --git a/Outputs/ScanTarget.hpp b/Outputs/ScanTarget.hpp
index 92899e0c3..0860af010 100644
--- a/Outputs/ScanTarget.hpp
+++ b/Outputs/ScanTarget.hpp
@@ -381,22 +381,22 @@ struct ScanTarget {
 
 struct ScanStatus {
 	/// The current (prediced) length of a field (including retrace).
-	Time::Seconds field_duration;
+	Time::Seconds field_duration = 0.0;
 	/// The difference applied to the field_duration estimate during the last field.
-	Time::Seconds field_duration_gradient;
+	Time::Seconds field_duration_gradient = 0.0;
 	/// The amount of time this device spends in retrace.
-	Time::Seconds retrace_duration;
+	Time::Seconds retrace_duration = 0.0;
 	/// The distance into the current field, from a small negative amount (in retrace) through
 	/// 0 (start of visible area field) to 1 (end of field).
 	///
 	/// This will increase monotonically, being a measure
 	/// of the current vertical position — i.e. if current_position = 0.8 then a caller can
 	/// conclude that the top 80% of the visible part of the display has been painted.
-	float current_position;
+	float current_position = 0.0f;
 	/// The total number of hsyncs so far encountered;
-	int hsync_count;
+	int hsync_count = 0;
 	/// @c true if retrace is currently going on; @c false otherwise.
-	bool is_in_retrace;
+	bool is_in_retrace = false;
 
 	/*!
 		@returns this ScanStatus, with time-relative fields scaled by dividing them by @c dividend.