diff --git a/OSBindings/Mac/Clock SignalTests/KlausDormannTests.swift b/OSBindings/Mac/Clock SignalTests/KlausDormannTests.swift
index 6a614019c..17dfda582 100644
--- a/OSBindings/Mac/Clock SignalTests/KlausDormannTests.swift	
+++ b/OSBindings/Mac/Clock SignalTests/KlausDormannTests.swift	
@@ -87,6 +87,10 @@ class KlausDormannTests: XCTestCase {
 				case 0x183a: return "STA (zp) acted as JAM"
 				case 0x1849: return "LDA/STA (zp) left flags in incorrect state"
 
+				case 0x1983: return "STZ didn't store zero"
+
+				case 0x1b03: return "BIT didn't set flags correctly"
+
 				case 0: return "Didn't find tests"
 				default: return "Unknown error at \(String(format:"%04x", address))"
 			}
diff --git a/Processors/6502/Implementation/6502Implementation.hpp b/Processors/6502/Implementation/6502Implementation.hpp
index ca0a371c6..d9888d29b 100644
--- a/Processors/6502/Implementation/6502Implementation.hpp
+++ b/Processors/6502/Implementation/6502Implementation.hpp
@@ -201,6 +201,7 @@ if(number_of_cycles <= Cycles(0)) break;
 					case OperationSTA:	operand_ = a_;											continue;
 					case OperationSTX:	operand_ = x_;											continue;
 					case OperationSTY:	operand_ = y_;											continue;
+					case OperationSTZ:	operand_ = 0;											continue;
 					case OperationSAX:	operand_ = a_ & x_;										continue;
 					case OperationSHA:	operand_ = a_ & x_ & (address_.bytes.high+1);			continue;
 					case OperationSHX:	operand_ = x_ & (address_.bytes.high+1);				continue;
diff --git a/Processors/6502/Implementation/6502Storage.cpp b/Processors/6502/Implementation/6502Storage.cpp
index 786394d45..49292b030 100644
--- a/Processors/6502/Implementation/6502Storage.cpp
+++ b/Processors/6502/Implementation/6502Storage.cpp
@@ -286,6 +286,12 @@ ProcessorStorage::ProcessorStorage(Personality personality) {
 		Install(0xb2, ZeroIndirectRead(OperationLDA));
 		Install(0xd2, ZeroIndirectRead(OperationCMP));
 		Install(0xd2, ZeroIndirectRead(OperationSBC));
+
+		// Add STZ.
+		Install(0x9c, AbsoluteWrite(OperationSTZ));
+		Install(0x9e, AbsoluteXWrite(OperationSTZ));
+		Install(0x64, ZeroWrite(OperationSTZ));
+		Install(0x74, ZeroXWrite(OperationSTZ));
 	}
 #undef Install
 }
diff --git a/Processors/6502/Implementation/6502Storage.hpp b/Processors/6502/Implementation/6502Storage.hpp
index 50d24727b..cde267786 100644
--- a/Processors/6502/Implementation/6502Storage.hpp
+++ b/Processors/6502/Implementation/6502Storage.hpp
@@ -49,7 +49,8 @@ class ProcessorStorage {
 			OperationIncrementOperand,					OperationORA,						OperationAND,							OperationEOR,
 			OperationINS,								OperationADC,						OperationSBC,							OperationLDA,
 			OperationLDX,								OperationLDY,						OperationLAX,							OperationSTA,
-			OperationSTX,								OperationSTY,						OperationSAX,							OperationSHA,
+			OperationSTX,								OperationSTY,						OperationSTZ,
+			OperationSAX,								OperationSHA,
 			OperationSHX,								OperationSHY,						OperationSHS,							OperationCMP,
 			OperationCPX,								OperationCPY,						OperationBIT,							OperationASL,
 			OperationASO,								OperationROL,						OperationRLA,							OperationLSR,