diff --git a/InstructionSets/PowerPC/Instruction.hpp b/InstructionSets/PowerPC/Instruction.hpp
index fd6c50a78..9cbf907f7 100644
--- a/InstructionSets/PowerPC/Instruction.hpp
+++ b/InstructionSets/PowerPC/Instruction.hpp
@@ -151,7 +151,15 @@ enum class Operation: uint8_t {
 	fnabsx, fnegx, fnmaddx, fnmaddsx, fnmsubx, fnmsubsx, frspx, fsubx, fsubsx,
 	icbi, isync, lbz, lbzu, lbzux, lbzx, lfd, lfdu, lfdux, lfdx, lfs, lfsu,
 	lfsux, lfsx, lha, lhau, lhaux, lhax, lhbrx, lhz, lhzu, lhzux, lhzx, lmw,
-	lswi, lswx, lwarx, lwbrx, lwz, lwzu, lwzux,
+	lswi, lswx, lwarx, lwbrx, lwz, lwzu,
+
+	/// Load word and zero with Update Indexed.
+	///
+	/// rD() = [ rA()|0 + rB() ]; and rA() is set to the calculated address.
+	///
+	/// PowerPC defines rA=0 and rA=rD to be invalid forms; the MPC601
+	/// will suppress the update if rA=0 or rA=rD.
+	lwzux,
 
 	/// Load word and zero indexed.
 	///
diff --git a/OSBindings/Mac/Clock SignalTests/DingusdevPowerPCTests.mm b/OSBindings/Mac/Clock SignalTests/DingusdevPowerPCTests.mm
index 2d1b6f79b..eceb73f53 100644
--- a/OSBindings/Mac/Clock SignalTests/DingusdevPowerPCTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/DingusdevPowerPCTests.mm	
@@ -19,6 +19,15 @@ using namespace InstructionSet::PowerPC;
 
 @implementation DingusdevPowerPCTests
 
+- (void)testABDInstruction:(Instruction)instruction columns:(NSArray<NSString *> *)columns testZero:(BOOL)testZero {
+	NSString *const rA = (instruction.rA() || !testZero) ? [NSString stringWithFormat:@"r%d", instruction.rA()] : @"0";
+	NSString *const rB = [NSString stringWithFormat:@"r%d", instruction.rB()];
+	NSString *const rD = [NSString stringWithFormat:@"r%d", instruction.rD()];
+	XCTAssertEqualObjects(rD, columns[3]);
+	XCTAssertEqualObjects(rA, columns[4]);
+	XCTAssertEqualObjects(rB, columns[5]);
+}
+
 - (void)testDecoding {
 	NSData *const testData =
 		[NSData dataWithContentsOfURL:
@@ -53,15 +62,15 @@ using namespace InstructionSet::PowerPC;
 				NSAssert(FALSE, @"Didn't handle %@", line);
 			break;
 
-			case Operation::lwzx: {
+			case Operation::lwzux:
+				XCTAssertEqualObjects(operation, @"lwzux");
+				[self testABDInstruction:instruction columns:columns testZero:YES];
+			break;
+
+			case Operation::lwzx:
 				XCTAssertEqualObjects(operation, @"lwzx");
-				NSString *const rA = instruction.rA() ? [NSString stringWithFormat:@"r%d", instruction.rA()] : @"0";
-				NSString *const rB = [NSString stringWithFormat:@"r%d", instruction.rB()];
-				NSString *const rD = [NSString stringWithFormat:@"r%d", instruction.rD()];
-				XCTAssertEqualObjects(rD, columns[3]);
-				XCTAssertEqualObjects(rA, columns[4]);
-				XCTAssertEqualObjects(rB, columns[5]);
-			} break;
+				[self testABDInstruction:instruction columns:columns testZero:YES];
+			break;
 
 			case Operation::bcx:
 			case Operation::bclrx: