diff --git a/Components/9918/9918.cpp b/Components/9918/9918.cpp
index e083eb071..8c94d72d3 100644
--- a/Components/9918/9918.cpp
+++ b/Components/9918/9918.cpp
@@ -106,7 +106,7 @@ void Base::reset_sprite_collection() {
 
 void Base::posit_sprite(int sprite_number, int sprite_position, int screen_row) {
 	if(!(status_ & StatusSpriteOverflow)) {
-		status_ = static_cast<uint8_t>((status_ & ~31) | sprite_number);
+		status_ = static_cast<uint8_t>((status_ & ~0x1f) | (sprite_number & 0x1f));
 	}
 	if(sprite_set_.sprites_stopped)
 		return;
@@ -891,7 +891,7 @@ void Base::draw_sms(int start, int end) {
 		for(int index = sprite_set_.fetched_sprite_slot - 1; index >= 0; --index) {
 			SpriteSet::ActiveSprite &sprite = sprite_set_.active_sprites[index];
 			if(sprite.shift_position < 16) {
-				int pixel_start = std::max(start, sprite.x);
+				const int pixel_start = std::max(start, sprite.x);
 
 				// TODO: it feels like the work below should be simplifiable;
 				// the double shift in particular, and hopefully the variable shift.
@@ -922,7 +922,8 @@ void Base::draw_sms(int start, int end) {
 			) colour_buffer[c] = sprite_buffer[c];
 		}
 
-		if(sprite_collision) status_ |= StatusSpriteCollision;
+		if(sprite_collision)
+			status_ |= StatusSpriteCollision;
 	}
 
 	// Map from the 32-colour buffer to real output pixels.
diff --git a/Components/9918/Implementation/9918Base.hpp b/Components/9918/Implementation/9918Base.hpp
index e3536f5d0..af2a2b1ee 100644
--- a/Components/9918/Implementation/9918Base.hpp
+++ b/Components/9918/Implementation/9918Base.hpp
@@ -12,6 +12,7 @@
 #include "../../../Outputs/CRT/CRT.hpp"
 #include "../../../ClockReceiver/ClockReceiver.hpp"
 
+#include <cassert>
 #include <cstdint>
 #include <memory>
 
@@ -593,7 +594,7 @@ class Base {
 		sprite_set_.active_sprites[sprite].x = \
 			ram_[\
 				sprite_attribute_table_address_ & size_t(0x3f80 | (sprite_set_.active_sprites[sprite].index << 1))\
-			] - (master_system_.shift_sprites_8px_left ? size_t(8) : size_t(0));	\
+			] - (master_system_.shift_sprites_8px_left ? 8 : 0);	\
 		const uint8_t name = ram_[\
 				sprite_attribute_table_address_ & size_t(0x3f81 | (sprite_set_.active_sprites[sprite].index << 1))\
 			] & (sprites_16x16_ ? ~1 : ~0);\
@@ -682,6 +683,8 @@ class Base {
 			// ... and do the actual fetching, which follows this routine:
 			switch(start) {
 				default:
+					assert(false);
+
 				sprite_fetch_block(0, 0);
 				sprite_fetch_block(6, 2);
 
@@ -712,9 +715,9 @@ class Base {
 				background_fetch_block(103, 16, 40, scrolled_row_info);
 				background_fetch_block(119, 20, 46, scrolled_row_info);
 				background_fetch_block(135, 24, 52, row_info);
-				background_fetch_block(152, 28, 58, row_info);
+				background_fetch_block(151, 28, 58, row_info);
 
-				external_slots_4(168);
+				external_slots_4(167);
 
 				return;
 			}