diff --git a/include/app/ParamWidget.hpp b/include/app/ParamWidget.hpp
index 0e28d0c7..e5ce9063 100644
--- a/include/app/ParamWidget.hpp
+++ b/include/app/ParamWidget.hpp
@@ -2,7 +2,7 @@
 #include "app/common.hpp"
 #include "widget/OpaqueWidget.hpp"
 #include "ui/Tooltip.hpp"
-#include "app/ParamQuantity.hpp"
+#include "engine/ParamQuantity.hpp"
 #include "history.hpp"
 
 
@@ -12,11 +12,10 @@ namespace app {
 
 /** Manages an engine::Param on a ModuleWidget. */
 struct ParamWidget : widget::OpaqueWidget {
-	ParamQuantity *paramQuantity = NULL;
+	engine::ParamQuantity *paramQuantity = NULL;
 	float dirtyValue = NAN;
 	ui::Tooltip *tooltip = NULL;
 
-	~ParamWidget();
 	void step() override;
 	void draw(const DrawArgs &args) override;
 	void onButton(const widget::ButtonEvent &e) override;
diff --git a/include/app/ParamQuantity.hpp b/include/engine/ParamQuantity.hpp
similarity index 95%
rename from include/app/ParamQuantity.hpp
rename to include/engine/ParamQuantity.hpp
index 4284a4b5..843a2823 100644
--- a/include/app/ParamQuantity.hpp
+++ b/include/engine/ParamQuantity.hpp
@@ -5,7 +5,7 @@
 
 
 namespace rack {
-namespace app {
+namespace engine {
 
 
 /** A Quantity that wraps an engine::Param. */
@@ -33,5 +33,5 @@ struct ParamQuantity : Quantity {
 };
 
 
-} // namespace app
+} // namespace engine
 } // namespace rack
diff --git a/include/helpers.hpp b/include/helpers.hpp
index 9a968159..1dfbb5b9 100644
--- a/include/helpers.hpp
+++ b/include/helpers.hpp
@@ -5,10 +5,10 @@
 #include "ui/MenuLabel.hpp"
 #include "ui/Menu.hpp"
 #include "app/PortWidget.hpp"
-#include "app/ParamQuantity.hpp"
 #include "app/ParamWidget.hpp"
 #include "app/Scene.hpp"
 #include "engine/Module.hpp"
+#include "engine/ParamQuantity.hpp"
 #include "app.hpp"
 #include "window.hpp"
 
@@ -66,7 +66,7 @@ TParamWidget *createParam(math::Vec pos, engine::Module *module, int paramId) {
 		if (f)
 			o->paramQuantity = f->create();
 		else
-			o->paramQuantity = new app::ParamQuantity;
+			o->paramQuantity = new engine::ParamQuantity;
 		o->paramQuantity->module = module;
 		o->paramQuantity->paramId = paramId;
 	}
diff --git a/src/ui/Quantity.cpp b/src/Quantity.cpp
similarity index 100%
rename from src/ui/Quantity.cpp
rename to src/Quantity.cpp
diff --git a/src/app/ParamWidget.cpp b/src/app/ParamWidget.cpp
index 8f6b3bf5..c542971e 100644
--- a/src/app/ParamWidget.cpp
+++ b/src/app/ParamWidget.cpp
@@ -2,7 +2,6 @@
 #include "ui/MenuOverlay.hpp"
 #include "ui/TextField.hpp"
 #include "app/Scene.hpp"
-#include "app/ParamQuantity.hpp"
 #include "app.hpp"
 #include "engine/Engine.hpp"
 #include "settings.hpp"
@@ -109,11 +108,6 @@ struct ParamUnmapItem : ui::MenuItem {
 };
 
 
-ParamWidget::~ParamWidget() {
-	if (paramQuantity)
-		delete paramQuantity;
-}
-
 void ParamWidget::step() {
 	if (paramQuantity) {
 		float value = paramQuantity->getValue();
diff --git a/src/app/ParamQuantity.cpp b/src/engine/ParamQuantity.cpp
similarity index 96%
rename from src/app/ParamQuantity.cpp
rename to src/engine/ParamQuantity.cpp
index b9243d4b..5c3542bf 100644
--- a/src/app/ParamQuantity.cpp
+++ b/src/engine/ParamQuantity.cpp
@@ -1,10 +1,10 @@
-#include "app/ParamQuantity.hpp"
+#include "engine/ParamQuantity.hpp"
 #include "app.hpp"
 #include "engine/Engine.hpp"
 
 
 namespace rack {
-namespace app {
+namespace engine {
 
 
 engine::Param *ParamQuantity::getParam() {
@@ -119,5 +119,5 @@ std::string ParamQuantity::getUnit() {
 }
 
 
-} // namespace app
+} // namespace engine
 } // namespace rack