diff --git a/apps/code/menu_controller.cpp b/apps/code/menu_controller.cpp
index 9a8afe1ed..be6460e9a 100644
--- a/apps/code/menu_controller.cpp
+++ b/apps/code/menu_controller.cpp
@@ -17,7 +17,7 @@ MenuController::MenuController(Responder * parentResponder, App * pythonDelegate
         MenuController * menu = (MenuController *)context;
         menu->consoleController()->setAutoImport(true);
         menu->stackViewController()->push(menu->consoleController());
-        return;
+        return true;
         }, this), KDFont::LargeFont),
   m_selectableTableView(this, this, this, this),
   m_scriptParameterController(nullptr, I18n::Message::ScriptOptions, this),
diff --git a/apps/exam_pop_up_controller.cpp b/apps/exam_pop_up_controller.cpp
index 364f95899..915fcf547 100644
--- a/apps/exam_pop_up_controller.cpp
+++ b/apps/exam_pop_up_controller.cpp
@@ -50,6 +50,7 @@ ExamPopUpController::ContentView::ContentView(Responder * parentResponder) :
     ExamPopUpController * controller = (ExamPopUpController *)context;
     Container * container = (Container *)controller->app()->container();
     container->activeApp()->dismissModalViewController();
+    return true;
   }, parentResponder), KDFont::SmallFont),
   m_okButton(parentResponder, I18n::Message::Ok, Invocation([](void * context, void * sender) {
     ExamPopUpController * controller = (ExamPopUpController *)context;
@@ -65,6 +66,7 @@ ExamPopUpController::ContentView::ContentView(Responder * parentResponder) :
     }
     container->refreshPreferences();
     container->activeApp()->dismissModalViewController();
+    return true;
   }, parentResponder), KDFont::SmallFont),
   m_warningTextView(KDFont::SmallFont, I18n::Message::Warning, 0.5, 0.5, KDColorWhite, KDColorBlack),
   m_messageTextView1(KDFont::SmallFont, I18n::Message::Default, 0.5, 0.5, KDColorWhite, KDColorBlack),
diff --git a/apps/hardware_test/pop_up_controller.cpp b/apps/hardware_test/pop_up_controller.cpp
index c0cb42ce2..92905900c 100644
--- a/apps/hardware_test/pop_up_controller.cpp
+++ b/apps/hardware_test/pop_up_controller.cpp
@@ -36,11 +36,13 @@ PopUpController::ContentView::ContentView(Responder * parentResponder) :
   m_cancelButton(this, I18n::Message::Cancel, Invocation([](void * context, void * sender) {
     PopUpController::ContentView * view = (PopUpController::ContentView *)context;
     view->app()->dismissModalViewController();
+    return true;
   }, this), KDFont::SmallFont),
   m_okButton(this, I18n::Message::Ok, Invocation([](void * context, void * sender) {
     PopUpController::ContentView * view = (PopUpController::ContentView *)context;
     AppsContainer * appsContainer = (AppsContainer *)view->app()->container();
     appsContainer->switchTo(appsContainer->hardwareTestAppSnapshot());
+    return true;
   }, this), KDFont::SmallFont),
   m_warningTextView(KDFont::SmallFont, I18n::Message::Warning, 0.5, 0.5, KDColorWhite, KDColorBlack),
   m_messageTextView1(KDFont::SmallFont, I18n::Message::HardwareTestLaunch1, 0.5, 0.5, KDColorWhite, KDColorBlack),
diff --git a/apps/sequence/list/list_controller.cpp b/apps/sequence/list/list_controller.cpp
index 947d03838..83e3c88b9 100644
--- a/apps/sequence/list/list_controller.cpp
+++ b/apps/sequence/list/list_controller.cpp
@@ -131,8 +131,10 @@ void ListController::editExpression(Sequence * sequence, int sequenceDefinition,
         InputViewController * myInputViewController = (InputViewController *)sender;
         const char * textBody = myInputViewController->textBody();
         mySequence->setContent(textBody);
+        return true; //TODO should return result of mySequence->setContent
         },
         [](void * context, void * sender){
+        return true;
       });
       break;
   case 1:
@@ -142,8 +144,10 @@ void ListController::editExpression(Sequence * sequence, int sequenceDefinition,
       InputViewController * myInputViewController = (InputViewController *)sender;
       const char * textBody = myInputViewController->textBody();
       mySequence->setFirstInitialConditionContent(textBody);
+      return true; //TODO should return result of mySequence->setFirstInitialConditionContent
       },
       [](void * context, void * sender){
+      return true;
     });
     break;
   default:
@@ -153,8 +157,10 @@ void ListController::editExpression(Sequence * sequence, int sequenceDefinition,
       InputViewController * myInputViewController = (InputViewController *)sender;
       const char * textBody = myInputViewController->textBody();
       mySequence->setSecondInitialConditionContent(textBody);
+      return true; //TODO should return the result of mySequence->setSecondInitialConditionContent
       },
       [](void * context, void * sender){
+      return true;
     });
   }
 }
diff --git a/apps/shared/expression_model_list_controller.cpp b/apps/shared/expression_model_list_controller.cpp
index 62a17b7b1..327a5ac3b 100644
--- a/apps/shared/expression_model_list_controller.cpp
+++ b/apps/shared/expression_model_list_controller.cpp
@@ -98,8 +98,10 @@ void ExpressionModelListController::editExpression(ExpressionModel * model, Ion:
     InputViewController * myInputViewController = (InputViewController *)sender;
     const char * textBody = myInputViewController->textBody();
     myModel->setContent(textBody);
+    return true; // TODO we should return a result from myModel->setContent, but we will remove ExpressionModelListController soon anyway
     },
     [](void * context, void * sender){
+    return true;
     });
 }
 
diff --git a/apps/shared/float_parameter_controller.cpp b/apps/shared/float_parameter_controller.cpp
index dfc33a6f4..5c8392ace 100644
--- a/apps/shared/float_parameter_controller.cpp
+++ b/apps/shared/float_parameter_controller.cpp
@@ -16,6 +16,7 @@ FloatParameterController::FloatParameterController(Responder * parentResponder)
   m_okButton(&m_selectableTableView, I18n::Message::Ok, Invocation([](void * context, void * sender) {
       FloatParameterController * parameterController = (FloatParameterController *) context;
       parameterController->buttonAction();
+      return true;
     }, this))
 {
 }
diff --git a/apps/shared/function_list_controller.cpp b/apps/shared/function_list_controller.cpp
index caefbe841..cc295e35d 100644
--- a/apps/shared/function_list_controller.cpp
+++ b/apps/shared/function_list_controller.cpp
@@ -13,11 +13,13 @@ FunctionListController::FunctionListController(Responder * parentResponder, Func
     FunctionListController * list = (FunctionListController *)context;
     TabViewController * tabController = list->tabController();
     tabController->setActiveTab(1);
+    return true;
   }, this), KDFont::SmallFont, Palette::PurpleBright),
   m_valuesButton(this, I18n::Message::DisplayValues, Invocation([](void * context, void * sender) {
     FunctionListController * list = (FunctionListController *)context;
     TabViewController * tabController = list->tabController();
     tabController->setActiveTab(2);
+    return true;
   }, this), KDFont::SmallFont, Palette::PurpleBright)
 {
   m_selectableTableView.setMargins(0);
diff --git a/apps/shared/interactive_curve_view_controller.cpp b/apps/shared/interactive_curve_view_controller.cpp
index 6bf52e420..d5a2e8083 100644
--- a/apps/shared/interactive_curve_view_controller.cpp
+++ b/apps/shared/interactive_curve_view_controller.cpp
@@ -18,16 +18,19 @@ InteractiveCurveViewController::InteractiveCurveViewController(Responder * paren
     InteractiveCurveViewController * graphController = (InteractiveCurveViewController *) context;
     StackViewController * stack = graphController->stackController();
     stack->push(graphController->rangeParameterController());
+    return true;
   }, this), KDFont::SmallFont),
   m_zoomButton(this, I18n::Message::Zoom, Invocation([](void * context, void * sender) {
     InteractiveCurveViewController * graphController = (InteractiveCurveViewController *) context;
     StackViewController * stack = graphController->stackController();
     stack->push(graphController->zoomParameterController());
+    return true;
   }, this), KDFont::SmallFont),
   m_defaultInitialisationButton(this, I18n::Message::Initialization, Invocation([](void * context, void * sender) {
     InteractiveCurveViewController * graphController = (InteractiveCurveViewController *) context;
     StackViewController * stack = graphController->stackController();
     stack->push(graphController->initialisationParameterController());
+    return true;
   }, this), KDFont::SmallFont)
 {
 }
diff --git a/apps/shared/storage_expression_model_list_controller.cpp b/apps/shared/storage_expression_model_list_controller.cpp
index bda47692c..9366f0f58 100644
--- a/apps/shared/storage_expression_model_list_controller.cpp
+++ b/apps/shared/storage_expression_model_list_controller.cpp
@@ -192,16 +192,17 @@ void StorageExpressionModelListController::editExpression(Ion::Events::Event eve
         StorageExpressionModelListController * myController = static_cast<StorageExpressionModelListController *>(context);
         InputViewController * myInputViewController = (InputViewController *)sender;
         const char * textBody = myInputViewController->textBody();
-        myController->editSelectedRecordWithText(textBody);
+        return myController->editSelectedRecordWithText(textBody);
       },
       [](void * context, void * sender){
+        return true;
       });
 }
 
-void StorageExpressionModelListController::editSelectedRecordWithText(const char * text) {
+bool StorageExpressionModelListController::editSelectedRecordWithText(const char * text) {
   Ion::Storage::Record record = modelStore()->recordAtIndex(modelIndexForRow(selectedRow()));
   ExpiringPointer<StorageExpressionModel> model =  modelStore()->modelForRecord(record);
-  model->setContent(text);
+  return (model->setContent(text) == Ion::Storage::Record::ErrorStatus::None);
 }
 
 bool StorageExpressionModelListController::removeModelRow(Ion::Storage::Record record) {
diff --git a/apps/shared/storage_expression_model_list_controller.h b/apps/shared/storage_expression_model_list_controller.h
index 43282e015..7b2353eae 100644
--- a/apps/shared/storage_expression_model_list_controller.h
+++ b/apps/shared/storage_expression_model_list_controller.h
@@ -26,7 +26,7 @@ protected:
   virtual void didChangeModelsList() {}
   virtual void reinitExpression(ExpiringPointer<StorageExpressionModel> model);
   virtual void editExpression(Ion::Events::Event event);
-  virtual void editSelectedRecordWithText(const char * text);
+  virtual bool editSelectedRecordWithText(const char * text);
   virtual bool removeModelRow(Ion::Storage::Record record);
   virtual int modelIndexForRow(int j) { return j; }
   virtual bool isAddEmptyRow(int j);
diff --git a/apps/shared/storage_function_list_controller.cpp b/apps/shared/storage_function_list_controller.cpp
index 1628b1000..a555a4c76 100644
--- a/apps/shared/storage_function_list_controller.cpp
+++ b/apps/shared/storage_function_list_controller.cpp
@@ -14,11 +14,13 @@ StorageFunctionListController::StorageFunctionListController(Responder * parentR
       StorageFunctionListController * list = (StorageFunctionListController *)context;
       TabViewController * tabController = list->tabController();
       tabController->setActiveTab(1);
+      return true;
     }, this), KDFont::SmallFont, Palette::PurpleBright),
   m_valuesButton(this, I18n::Message::DisplayValues, Invocation([](void * context, void * sender) {
       StorageFunctionListController * list = (StorageFunctionListController *)context;
       TabViewController * tabController = list->tabController();
       tabController->setActiveTab(2);
+      return true;
     }, this), KDFont::SmallFont, Palette::PurpleBright),
   m_titlesColumnWidth(k_minTitleColumnWidth)
 {
diff --git a/apps/shared/storage_values_controller.cpp b/apps/shared/storage_values_controller.cpp
index 99f4606dc..4a7558ee7 100644
--- a/apps/shared/storage_values_controller.cpp
+++ b/apps/shared/storage_values_controller.cpp
@@ -23,6 +23,7 @@ StorageValuesController::StorageValuesController(Responder * parentResponder, In
     StorageValuesController * valuesController = (StorageValuesController *) context;
     StackViewController * stack = ((StackViewController *)valuesController->stackController());
     stack->push(valuesController->intervalParameterController());
+    return true;
   }, this), k_font)
 {
   m_selectableTableView.setVerticalCellOverlap(0);
diff --git a/apps/shared/values_controller.cpp b/apps/shared/values_controller.cpp
index ce3fd76a4..5a57c738a 100644
--- a/apps/shared/values_controller.cpp
+++ b/apps/shared/values_controller.cpp
@@ -23,6 +23,7 @@ ValuesController::ValuesController(Responder * parentResponder, InputEventHandle
     ValuesController * valuesController = (ValuesController *) context;
     StackViewController * stack = ((StackViewController *)valuesController->stackController());
     stack->push(valuesController->intervalParameterController());
+    return true;
   }, this), KDFont::SmallFont)
 {
   m_selectableTableView.setVerticalCellOverlap(0);
diff --git a/apps/solver/list_controller.cpp b/apps/solver/list_controller.cpp
index 191551ebf..28d6b0d22 100644
--- a/apps/solver/list_controller.cpp
+++ b/apps/solver/list_controller.cpp
@@ -15,6 +15,7 @@ ListController::ListController(Responder * parentResponder, EquationStore * equa
   m_resolveButton(this, equationStore->numberOfDefinedModels() > 1 ? I18n::Message::ResolveSystem : I18n::Message::ResolveEquation, Invocation([](void * context, void * sender) {
     ListController * list = (ListController *)context;
     list->resolveEquations();
+    return true;
   }, this), KDFont::LargeFont, Palette::PurpleBright),
   m_modelsParameterController(this, equationStore, this),
   m_modelsStackController(nullptr, &m_modelsParameterController, KDColorWhite, Palette::PurpleDark, Palette::PurpleDark)
diff --git a/escher/include/escher/invocation.h b/escher/include/escher/invocation.h
index 7e7c2fd65..e82cbb128 100644
--- a/escher/include/escher/invocation.h
+++ b/escher/include/escher/invocation.h
@@ -3,9 +3,9 @@
 
 class Invocation {
 public:
-  typedef void (*Action)(void * context, void * sender);
+  typedef bool (*Action)(void * context, void * sender);
   Invocation(Action a, void * c);
-  void perform(void * sender);
+  bool perform(void * sender);
 private:
   Action m_action;
   void * m_context;
diff --git a/escher/src/invocation.cpp b/escher/src/invocation.cpp
index 8b7140796..80ab77c10 100644
--- a/escher/src/invocation.cpp
+++ b/escher/src/invocation.cpp
@@ -1,11 +1,11 @@
 #include <escher/invocation.h>
 
 Invocation::Invocation(Action a, void * c) :
-	m_action(a),
-	m_context(c)
+  m_action(a),
+  m_context(c)
 {
 }
 
-void Invocation::perform(void * sender) {
-	(*m_action)(m_context, sender);
+bool Invocation::perform(void * sender) {
+  return (*m_action)(m_context, sender);
 }