Index: source/gui/Scripting/JSInterface_GUIProxy.h
===================================================================
--- source/gui/Scripting/JSInterface_GUIProxy.h
+++ source/gui/Scripting/JSInterface_GUIProxy.h
@@ -97,9 +97,9 @@
 		return true;
 	}
 	// Return nothing.
-	virtual bool enumerate(JSContext* UNUSED(cx), JS::HandleObject UNUSED(proxy), JS::MutableHandleObject UNUSED(objp)) const override
+	virtual JSObject* enumerate(JSContext* UNUSED(cx), JS::HandleObject UNUSED(proxy)) const override
 	{
-		return true;
+		return nullptr;
 	}
 	// Throw an exception is JS attempts to query the prototype.
 	virtual bool getPrototypeIfOrdinary(JSContext* UNUSED(cx), JS::HandleObject UNUSED(proxy), bool* UNUSED(isOrdinary), JS::MutableHandleObject UNUSED(protop)) const override
Index: source/gui/Scripting/JSInterface_GUIProxy_impl.h
===================================================================
--- source/gui/Scripting/JSInterface_GUIProxy_impl.h
+++ source/gui/Scripting/JSInterface_GUIProxy_impl.h
@@ -20,7 +20,7 @@
 template <typename T>
 js::Class& JSI_GUIProxy<T>::ClassDefinition()
 {
-	static js::Class c = PROXY_CLASS_DEF("GUIObjectProxy", JSCLASS_HAS_PRIVATE | JSCLASS_HAS_CACHED_PROTO(JSProto_Proxy));
+	static js::Class c = PROXY_CLASS_DEF("GUIObjectProxy", JSCLASS_HAS_PRIVATE | JSCLASS_HAS_CACHED_PROTO(JSProto_Proxy) | JSCLASS_HAS_RESERVED_SLOTS(1));
 	return c;
 }
 
Index: source/gui/Scripting/JSInterface_GUISize.cpp
===================================================================
--- source/gui/Scripting/JSInterface_GUISize.cpp
+++ source/gui/Scripting/JSInterface_GUISize.cpp
@@ -30,7 +30,7 @@
 	nullptr, nullptr,
 	nullptr, nullptr,
 	nullptr, nullptr, nullptr, nullptr,
-	nullptr, nullptr, JSI_GUISize::construct, nullptr
+	nullptr, JSI_GUISize::construct, nullptr
 };
 
 JSFunctionSpec JSI_GUISize::JSI_methods[] =
Index: source/scriptinterface/ScriptContext.cpp
===================================================================
--- source/scriptinterface/ScriptContext.cpp
+++ source/scriptinterface/ScriptContext.cpp
@@ -27,15 +27,13 @@
 
 void GCSliceCallbackHook(JSContext* UNUSED(cx), JS::GCProgress progress, const JS::GCDescription& UNUSED(desc))
 {
-	/*
-	 * During non-incremental GC, the GC is bracketed by JSGC_CYCLE_BEGIN/END
-	 * callbacks. During an incremental GC, the sequence of callbacks is as
-	 * follows:
-	 *   JSGC_CYCLE_BEGIN, JSGC_SLICE_END  (first slice)
-	 *   JSGC_SLICE_BEGIN, JSGC_SLICE_END  (second slice)
-	 *   ...
-	 *   JSGC_SLICE_BEGIN, JSGC_CYCLE_END  (last slice)
-	*/
+	/**
+	 * From the GCAPI.h file:
+	 * > During GC, the GC is bracketed by GC_CYCLE_BEGIN/END callbacks. Each
+	 * > slice between those (whether an incremental or the sole non-incremental
+	 * > slice) is bracketed by GC_SLICE_BEGIN/GC_SLICE_END.
+	 * Thus, to safely monitor GCs, we need to profile SLICE_X calls.
+	 */
 
 
 	if (progress == JS::GC_SLICE_BEGIN)
@@ -48,19 +46,7 @@
 	{
 		if (CProfileManager::IsInitialised() && ThreadUtil::IsMainThread())
 			g_Profiler.Stop();
-    	g_Profiler2.RecordRegionLeave();
-	}
-	else if (progress == JS::GC_CYCLE_BEGIN)
-	{
-		if (CProfileManager::IsInitialised() && ThreadUtil::IsMainThread())
-			g_Profiler.Start("GCSlice");
-		g_Profiler2.RecordRegionEnter("GCSlice");
-	}
-	else if (progress == JS::GC_CYCLE_END)
-	{
-		if (CProfileManager::IsInitialised() && ThreadUtil::IsMainThread())
-			g_Profiler.Stop();
-    	g_Profiler2.RecordRegionLeave();
+		g_Profiler2.RecordRegionLeave();
 	}
 
 	// The following code can be used to print some information aobut garbage collection
@@ -219,7 +205,7 @@
 					printf("Finishing incremental GC because gcBytes > m_ContextSize / 2. \n");
 #endif
 					PrepareCompartmentsForIncrementalGC();
-					JS::FinishIncrementalGC(m_cx, JS::gcreason::REFRESH_FRAME);
+					JS::FinishIncrementalGC(m_cx, JS::gcreason::API);
 				}
 				else
 				{
@@ -249,9 +235,9 @@
 #endif
 				PrepareCompartmentsForIncrementalGC();
 				if (!JS::IsIncrementalGCInProgress(m_cx))
-					JS::StartIncrementalGC(m_cx, GC_NORMAL, JS::gcreason::REFRESH_FRAME, GCSliceTimeBudget);
+					JS::StartIncrementalGC(m_cx, GC_NORMAL, JS::gcreason::API, GCSliceTimeBudget);
 				else
-					JS::IncrementalGCSlice(m_cx, JS::gcreason::REFRESH_FRAME, GCSliceTimeBudget);
+					JS::IncrementalGCSlice(m_cx, JS::gcreason::API, GCSliceTimeBudget);
 			}
 			m_LastGCBytes = gcBytes;
 		}
@@ -262,7 +248,7 @@
 {
 	JS_SetGCParameter(m_cx, JSGC_MODE, JSGC_MODE_ZONE);
 	JS::PrepareForFullGC(m_cx);
-	JS::GCForReason(m_cx, GC_SHRINK, JS::gcreason::REFRESH_FRAME);
+	JS::GCForReason(m_cx, GC_SHRINK, JS::gcreason::API);
 	JS_SetGCParameter(m_cx, JSGC_MODE, JSGC_MODE_INCREMENTAL);
 }
 
Index: source/scriptinterface/ScriptInterface.cpp
===================================================================
--- source/scriptinterface/ScriptInterface.cpp
+++ source/scriptinterface/ScriptInterface.cpp
@@ -98,7 +98,7 @@
 	nullptr, nullptr,
 	nullptr, nullptr,
 	nullptr, nullptr, nullptr,
-	nullptr, nullptr, nullptr, nullptr,
+	nullptr, nullptr, nullptr,
 	JS_GlobalObjectTraceHook
 };
 
@@ -327,10 +327,7 @@
 	JS::CompartmentCreationOptions creationOpt;
 	// Keep JIT code during non-shrinking GCs. This brings a quite big performance improvement.
 	creationOpt.setPreserveJitCode(true);
-	JS::CompartmentBehaviors behaviors;
-	behaviors.setVersion(JSVERSION_LATEST);
-
-	JS::CompartmentOptions opt(creationOpt, behaviors);
+	JS::CompartmentOptions opt(creationOpt, JS::CompartmentBehaviors{});
 
 	JSAutoRequest rq(m_cx);
 	m_glob = JS_NewGlobalObject(m_cx, &global_class, nullptr, JS::OnNewGlobalHookOption::FireOnNewGlobalHook, opt);
@@ -494,7 +491,7 @@
 	                                           ps, fs,                   // Properties, methods
 	                                           static_ps, static_fs));   // Constructor properties, methods
 
-	if (obj == NULL)
+	if (obj == nullptr)
 	{
 		ScriptException::CatchPending(rq);
 		throw PSERROR_Scripting_DefineType_CreationFailed();
Index: source/scriptinterface/tests/test_ScriptInterface.h
===================================================================
--- source/scriptinterface/tests/test_ScriptInterface.h
+++ source/scriptinterface/tests/test_ScriptInterface.h
@@ -40,7 +40,7 @@
 		ScriptInterface script("Test", "Test", g_ScriptContext);
 		TestLogger logger;
 		TS_ASSERT(!script.LoadScript(L"test.js", "1+"));
-		TS_ASSERT_STR_CONTAINS(logger.GetOutput(), "ERROR: JavaScript error: test.js line 1\nexpected expression, got end of script");
+		TS_ASSERT_STR_CONTAINS(logger.GetOutput(), "ERROR: JavaScript error: test.js line 3\nexpected expression, got \'}\'");
 	}
 
 	void test_loadscript_strict_warning()
@@ -57,7 +57,7 @@
 		ScriptInterface script("Test", "Test", g_ScriptContext);
 		TestLogger logger;
 		TS_ASSERT(!script.LoadScript(L"test.js", "with(1){}"));
-		TS_ASSERT_STR_CONTAINS(logger.GetOutput(), "ERROR: JavaScript error: test.js line 1\nstrict mode code may not contain \'with\' statements");
+		TS_ASSERT_STR_CONTAINS(logger.GetOutput(), "ERROR: JavaScript error: test.js line 2\nstrict mode code may not contain \'with\' statements");
 	}
 
 	void test_clone_basic()
Index: source/simulation2/serialization/BinarySerializer.cpp
===================================================================
--- source/simulation2/serialization/BinarySerializer.cpp
+++ source/simulation2/serialization/BinarySerializer.cpp
@@ -68,7 +68,7 @@
 
 	switch (JS_TypeOfValue(rq.cx, val))
 	{
-	case JSTYPE_VOID:
+	case JSTYPE_UNDEFINED:
 	{
 		m_Serializer.NumberU8_Unbounded("type", SCRIPT_TYPE_VOID);
 		break;