diff --git a/include/engine/Module.hpp b/include/engine/Module.hpp
index 8e9d4847..bf3a4ff1 100644
--- a/include/engine/Module.hpp
+++ b/include/engine/Module.hpp
@@ -13,7 +13,7 @@ namespace rack {
 
 
 struct Module {
-	int id = -1;
+	int id = 0;
 	std::vector<Param> params;
 	std::vector<Input> inputs;
 	std::vector<Output> outputs;
diff --git a/include/engine/Wire.hpp b/include/engine/Wire.hpp
index 82b99caa..8559966b 100644
--- a/include/engine/Wire.hpp
+++ b/include/engine/Wire.hpp
@@ -7,6 +7,7 @@ namespace rack {
 
 
 struct Wire {
+	int id = 0;
 	Module *outputModule = NULL;
 	int outputId;
 	Module *inputModule = NULL;
diff --git a/src/app/RackWidget.cpp b/src/app/RackWidget.cpp
index 8f6da323..7b5b252b 100644
--- a/src/app/RackWidget.cpp
+++ b/src/app/RackWidget.cpp
@@ -235,7 +235,7 @@ json_t *RackWidget::toJson() {
 	json_object_set_new(rootJ, "modules", modulesJ);
 
 	// wires
-	json_t *wires = json_array();
+	json_t *wiresJ = json_array();
 	for (Widget *w : wireContainer->children) {
 		WireWidget *wireWidget = dynamic_cast<WireWidget*>(w);
 		assert(wireWidget);
@@ -245,20 +245,24 @@ json_t *RackWidget::toJson() {
 		// Only serialize WireWidgets connected on both ends
 		if (!(outputPort && inputPort))
 			continue;
+
+		Wire *wire = wireWidget->wire;
+		assert(wire);
 		// wire
-		json_t *wire = wireWidget->toJson();
+		json_t *wireJ = wireWidget->toJson();
 
 		assert(outputPort->module);
 		assert(inputPort->module);
 
-		json_object_set_new(wire, "outputModuleId", json_integer(outputPort->module->id));
-		json_object_set_new(wire, "outputId", json_integer(outputPort->portId));
-		json_object_set_new(wire, "inputModuleId", json_integer(inputPort->module->id));
-		json_object_set_new(wire, "inputId", json_integer(inputPort->portId));
+		json_object_set_new(wireJ, "id", json_integer(wire->id));
+		json_object_set_new(wireJ, "outputModuleId", json_integer(outputPort->module->id));
+		json_object_set_new(wireJ, "outputId", json_integer(outputPort->portId));
+		json_object_set_new(wireJ, "inputModuleId", json_integer(inputPort->module->id));
+		json_object_set_new(wireJ, "inputId", json_integer(inputPort->portId));
 
-		json_array_append_new(wires, wire);
+		json_array_append_new(wiresJ, wireJ);
 	}
-	json_object_set_new(rootJ, "wires", wires);
+	json_object_set_new(rootJ, "wires", wiresJ);
 
 	return rootJ;
 }
@@ -306,7 +310,7 @@ void RackWidget::fromJson(json_t *rootJ) {
 		if (moduleWidget) {
 			// id
 			json_t *idJ = json_object_get(moduleJ, "id");
-			int id = -1;
+			int id = 0;
 			if (idJ)
 				id = json_integer_value(idJ);
 			// pos
diff --git a/src/engine/Engine.cpp b/src/engine/Engine.cpp
index c4b31ec8..d5d726ae 100644
--- a/src/engine/Engine.cpp
+++ b/src/engine/Engine.cpp
@@ -52,7 +52,8 @@ struct Engine::Internal {
 
 	Module *resetModule = NULL;
 	Module *randomizeModule = NULL;
-	int nextModuleId = 0;
+	int nextModuleId = 1;
+	int nextWireId = 1;
 
 	// Parameter smoothing
 	Module *smoothModule = NULL;
@@ -218,7 +219,7 @@ void Engine::addModule(Module *module) {
 	VIPLock vipLock(internal->vipMutex);
 	std::lock_guard<std::mutex> lock(internal->mutex);
 	// Set ID
-	assert(module->id == -1);
+	assert(module->id == 0);
 	module->id = internal->nextModuleId++;
 	// Check that the module is not already added
 	auto it = std::find(modules.begin(), modules.end(), module);
@@ -245,7 +246,7 @@ void Engine::removeModule(Module *module) {
 	// Remove the module
 	modules.erase(it);
 	// Remove id
-	module->id = -1;
+	module->id = 0;
 }
 
 void Engine::resetModule(Module *module) {
@@ -285,6 +286,9 @@ void Engine::addWire(Wire *wire) {
 		assert(wire2 != wire);
 		assert(!(wire2->inputModule == wire->inputModule && wire2->inputId == wire->inputId));
 	}
+	// Set ID
+	assert(wire->id == 0);
+	wire->id = internal->nextWireId++;
 	// Add the wire
 	wires.push_back(wire);
 	Engine_updateActive(this);
@@ -302,6 +306,8 @@ void Engine::removeWire(Wire *wire) {
 	// Remove the wire
 	wires.erase(it);
 	Engine_updateActive(this);
+	// Remove ID
+	wire->id = 0;
 }
 
 void Engine::setParam(Module *module, int paramId, float value) {