diff --git a/Machines/Commodore/Plus4/Plus4.cpp b/Machines/Commodore/Plus4/Plus4.cpp
index 9c18940e5..3e7279970 100644
--- a/Machines/Commodore/Plus4/Plus4.cpp
+++ b/Machines/Commodore/Plus4/Plus4.cpp
@@ -174,7 +174,7 @@ public:
 			if(isReadOperation(operation)) {
 				switch(address) {
 					case 0xff00:	*value = timers_.read<0>();		break;
-					case 0xff01:	*value = timers_.read<1	>();	break;
+					case 0xff01:	*value = timers_.read<1>();		break;
 					case 0xff02:	*value = timers_.read<2>();		break;
 					case 0xff03:	*value = timers_.read<3>();		break;
 					case 0xff04:	*value = timers_.read<4>();		break;
diff --git a/Machines/Commodore/Plus4/Video.hpp b/Machines/Commodore/Plus4/Video.hpp
index 4db263222..ba91923e2 100644
--- a/Machines/Commodore/Plus4/Video.hpp
+++ b/Machines/Commodore/Plus4/Video.hpp
@@ -191,7 +191,7 @@ public:
 			}
 
 			const auto next = Numeric::upper_bound<
-				0, 3, 288, 290, 296, 304, 307, 315, 328, 336, 344, 358, 376, 384, 390, 400, 416, 424, 432, 440, 451, 465
+				0, 3, 288, 290, 296, 304, 307, 315, 328, 336, 344, 358, 368, 376, 384, 390, 400, 416, 424, 432, 440, 451, 465
 			>(horizontal_counter_);
 			const auto period = std::min(next - horizontal_counter_, ticks_remaining);
 
@@ -295,7 +295,13 @@ public:
 				case 408:	horizontal_burst_ = false;	break;	// Burst end.
 				case 416:	horizontal_blank_ = false;	break;	// Horizontal blanking end.
 
-				case 424:	// Increment character position reload.
+				case 368:
+					if(raster_interrupt_ == vertical_counter_) {
+						interrupts_.apply(Interrupts::Flag::Raster);
+					}
+				break;
+
+				case 424:	// Increment character position reload; also interrput time.
 				break;
 
 				case 440:	// Video shift register start.
diff --git a/Numeric/UpperBound.hpp b/Numeric/UpperBound.hpp
index f00d08a80..bc735ca5e 100644
--- a/Numeric/UpperBound.hpp
+++ b/Numeric/UpperBound.hpp
@@ -16,7 +16,7 @@ namespace Numeric {
 /// E.g. @c at_index<0, 3, 5, 6, 7, 8, 9>() returns the `3 - 0` = 4th element from the
 /// list 5, 6, 7, 8, 9, i.e. 8.
 template<int origin, int index, int T, int... Args>
-int at_index() {
+constexpr int at_index() {
 	if constexpr (origin == index || sizeof...(Args) == 0) {
 		return T;
 	} else {
@@ -40,10 +40,22 @@ int upper_bound_bounded(int location) {
 	}
 }
 
+template <int index, int... Args>
+constexpr int is_ordered() {
+	if constexpr (sizeof...(Args) == index + 1) {
+		return true;
+	} else {
+		return
+			(at_index<0, index, Args...>() < at_index<0, index+1, Args...>()) &&
+			is_ordered<index+1, Args...>();
+	}
+}
+
 /// @returns The result of binary searching for the first thing in the template arguments
 /// is strictly greater than @c location.
 template <int... Args>
 int upper_bound(int location) {
+	static_assert(is_ordered<0, Args...>(), "Template arguments must be in ascending order.");
 	return upper_bound_bounded<0, sizeof...(Args), Args...>(location);
 }