diff --git a/Components/OPL2/OPL2.cpp b/Components/OPL2/OPL2.cpp
index 190688f8c..4ed8bd237 100644
--- a/Components/OPL2/OPL2.cpp
+++ b/Components/OPL2/OPL2.cpp
@@ -455,7 +455,7 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
 			}
 
 			// Two possible terminating conditions: (i) the attack rate is 15; (ii) full volume has been reached.
-			if(attack_rate > 60 || state.adsr_attenuation_ < 0) {
+			if(attack_rate > 60 || state.adsr_attenuation_ <= 0) {
 				state.adsr_attenuation_ = 0;
 				state.adsr_phase_ = OperatorState::ADSRPhase::Decay;
 			}
diff --git a/Components/OPL2/OPL2.hpp b/Components/OPL2/OPL2.hpp
index 647cc3ff5..398eead6d 100644
--- a/Components/OPL2/OPL2.hpp
+++ b/Components/OPL2/OPL2.hpp
@@ -27,7 +27,7 @@ namespace OPL {
 struct OperatorState {
 	public:
 		int phase = 0;			// Will be in the range [0, 1023], mapping into a 1024-unit sine curve.
-		int attenuation = 255;	// Will be in the range [0, 1023].
+		int attenuation = 1023;	// Will be in the range [0, 1023].
 
 	private:
 		int divider_ = 0;
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 293c7274e..ca3b78ee1 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -777,6 +777,7 @@
 		4BBFBB6C1EE8401E00C01E7A /* ZX8081.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BBFBB6A1EE8401E00C01E7A /* ZX8081.cpp */; };
 		4BBFE83D21015D9C00BF1C40 /* CSJoystickManager.m in Sources */ = {isa = PBXBuildFile; fileRef = 4BBFE83C21015D9C00BF1C40 /* CSJoystickManager.m */; };
 		4BBFFEE61F7B27F1005F3FEB /* TrackSerialiser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BBFFEE51F7B27F1005F3FEB /* TrackSerialiser.cpp */; };
+		4BC0CB282446BC7B00A79DBB /* OPLTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4BC0CB272446BC7B00A79DBB /* OPLTests.mm */; };
 		4BC131702346DE5000E4FF3D /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC1316F2346DE5000E4FF3D /* StaticAnalyser.cpp */; };
 		4BC131712346DE5000E4FF3D /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC1316F2346DE5000E4FF3D /* StaticAnalyser.cpp */; };
 		4BC131762346DE9100E4FF3D /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC131752346DE9100E4FF3D /* StaticAnalyser.cpp */; };
@@ -1648,6 +1649,7 @@
 		4BBFE83C21015D9C00BF1C40 /* CSJoystickManager.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = CSJoystickManager.m; sourceTree = "<group>"; };
 		4BBFE83E21015DAE00BF1C40 /* CSJoystickManager.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = CSJoystickManager.h; sourceTree = "<group>"; };
 		4BBFFEE51F7B27F1005F3FEB /* TrackSerialiser.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = TrackSerialiser.cpp; sourceTree = "<group>"; };
+		4BC0CB272446BC7B00A79DBB /* OPLTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = OPLTests.mm; sourceTree = "<group>"; };
 		4BC1316D2346DE5000E4FF3D /* StaticAnalyser.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = StaticAnalyser.hpp; sourceTree = "<group>"; };
 		4BC1316E2346DE5000E4FF3D /* Target.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Target.hpp; sourceTree = "<group>"; };
 		4BC1316F2346DE5000E4FF3D /* StaticAnalyser.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = StaticAnalyser.cpp; sourceTree = "<group>"; };
@@ -3339,6 +3341,7 @@
 		4BB73EB51B587A5100552FC2 /* Clock SignalTests */ = {
 			isa = PBXGroup;
 			children = (
+				4BC0CB272446BC7B00A79DBB /* OPLTests.mm */,
 				4B85322922778E4200F26553 /* Comparative68000.hpp */,
 				4B90467222C6FA31000E2074 /* TestRunner68000.hpp */,
 				4B97ADC722C6FD9B00A22A41 /* 68000ArithmeticTests.mm */,
@@ -4729,6 +4732,7 @@
 				4B778F5523A5F2A70000D260 /* Keyboard.cpp in Sources */,
 				4B778F5D23A5F3230000D260 /* Commodore.cpp in Sources */,
 				4B98A05F1FFAD62400ADF63B /* CSROMFetcher.mm in Sources */,
+				4BC0CB282446BC7B00A79DBB /* OPLTests.mm in Sources */,
 				4BC9E1EE1D23449A003FCEE4 /* 6502InterruptTests.swift in Sources */,
 				4BEF6AAA1D35CE9E00E73575 /* DigitalPhaseLockedLoopBridge.mm in Sources */,
 				4B778F3123A5F0CB0000D260 /* Keyboard.cpp in Sources */,
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme
index f049730f4..63be2c037 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
@@ -23,9 +23,9 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
-      buildConfiguration = "Release"
-      selectedDebuggerIdentifier = ""
-      selectedLauncherIdentifier = "Xcode.IDEFoundation.Launcher.PosixSpawn"
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES"
       disableMainThreadChecker = "YES"
       codeCoverageEnabled = "YES">
diff --git a/OSBindings/Mac/Clock SignalTests/OPLTests.mm b/OSBindings/Mac/Clock SignalTests/OPLTests.mm
index aad765787..1c39fe0b4 100644
--- a/OSBindings/Mac/Clock SignalTests/OPLTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/OPLTests.mm	
@@ -20,7 +20,21 @@
 	Yamaha::OPL::Operator test_operator;
 	Yamaha::OPL::OperatorState test_state;
 
-	
+	test_operator.set_attack_decay(0x88);
+	test_operator.set_sustain_release(0x88);
+
+	// While key is off, ADSR attenuation should remain above 511.
+	for(int c = 0; c < 1024; ++c) {
+		test_operator.update(test_state, false, 0, 0);
+		XCTAssertGreaterThanOrEqual(test_state.attenuation, 511);
+	}
+
+	// Set key on...
+	for(int c = 0; c < 4096; ++c) {
+		test_operator.update(test_state, true, 0, 0);
+		NSLog(@"%d", test_state.attenuation);
+	}
+
 }
 
 @end