diff --git a/apps/sequence/app.cpp b/apps/sequence/app.cpp
index b5ef4253e..3f01d17bc 100644
--- a/apps/sequence/app.cpp
+++ b/apps/sequence/app.cpp
@@ -67,4 +67,11 @@ Shared::SequenceContext * App::localContext() {
   return &m_sequenceContext;
 }
 
+NestedMenuController * App::variableBoxForInputEventHandler(InputEventHandler * textInput) {
+  MathVariableBoxController * varBox = AppsContainer::sharedAppsContainer()->variableBoxController();
+  varBox->setSender(textInput);
+  varBox->lockDeleteEvent(MathVariableBoxController::Page::Sequence);
+  return varBox;
+}
+
 }
diff --git a/apps/sequence/app.h b/apps/sequence/app.h
index 834c8d3ce..be61dd8cb 100644
--- a/apps/sequence/app.h
+++ b/apps/sequence/app.h
@@ -47,6 +47,7 @@ public:
   // TODO: override variableBoxForInputEventHandler to lock sequence in the variable box once they appear there
   // NestedMenuController * variableBoxForInputEventHandler(InputEventHandler * textInput) override;
   CodePoint XNT() override { return 'n'; }
+  NestedMenuController * variableBoxForInputEventHandler(InputEventHandler * textInput) override;
   Shared::SequenceContext * localContext() override;
   Shared::SequenceStore * functionStore() override { return static_cast<Shared::GlobalContext *>(AppsContainer::sharedAppsContainer()->globalContext())->sequenceStore(); }
   Shared::Interval * interval() { return snapshot()->interval(); }
diff --git a/apps/shared/cache_context.cpp b/apps/shared/cache_context.cpp
index 0758ba9b4..3fcf76f43 100644
--- a/apps/shared/cache_context.cpp
+++ b/apps/shared/cache_context.cpp
@@ -30,12 +30,14 @@ const Expression CacheContext<T>::expressionForSymbolAbstract(const Poincare::Sy
       return Float<T>::Builder(m_values[index][1]);
     }
     Ion::Storage::Record record = m_sequenceContext->sequenceStore()->recordAtIndex(index);
-    Sequence * seq = m_sequenceContext->sequenceStore()->modelForRecord(record);
-    rank.replaceSymbolWithExpression(Symbol::Builder(UCodePointUnknown), Float<T>::Builder(m_nValue));
-    T n = PoincareHelpers::ApproximateToScalar<T>(rank, this);
-    // In case the rank is not int or sequence referenced is not defined, return NAN
-    if (std::floor(n) == n && seq->fullName() != nullptr) {
-      return Float<T>::Builder(seq->valueAtRank<T>(n, m_sequenceContext));
+    if (!record.isNull()) {
+      Sequence * seq = m_sequenceContext->sequenceStore()->modelForRecord(record);
+      rank.replaceSymbolWithExpression(Symbol::Builder(UCodePointUnknown), Float<T>::Builder(m_nValue));
+      T n = PoincareHelpers::ApproximateToScalar<T>(rank, this);
+      // In case the rank is not int or sequence referenced is not defined, return NAN
+      if (std::floor(n) == n && seq->fullName() != nullptr) {
+        return Float<T>::Builder(seq->valueAtRank<T>(n, m_sequenceContext));
+      }
     } else {
       return Float<T>::Builder(NAN);
     }
diff --git a/apps/shared/expression_model.h b/apps/shared/expression_model.h
index b57ae5ac2..6fe6501a3 100644
--- a/apps/shared/expression_model.h
+++ b/apps/shared/expression_model.h
@@ -22,6 +22,7 @@ public:
   Ion::Storage::Record::ErrorStatus setExpressionContent(Ion::Storage::Record * record, const Poincare::Expression & newExpression);
 
   virtual void tidy() const;
+  bool hasValidExpression() { return !m_expression.isUninitialized(); }
 protected:
   // Setters helper
   static Poincare::Expression BuildExpressionFromText(const char * c, CodePoint symbol = 0, Poincare::Context * context = nullptr);
diff --git a/apps/shared/global_context.cpp b/apps/shared/global_context.cpp
index b5b6d6fe2..654c7737b 100644
--- a/apps/shared/global_context.cpp
+++ b/apps/shared/global_context.cpp
@@ -127,7 +127,7 @@ const Expression GlobalContext::ExpressionForSequence(const SymbolAbstract & sym
   char unknownN[bufferSize];
   Poincare::SerializationHelper::CodePoint(unknownN, bufferSize, UCodePointUnknown);
   float rank = symbol.childAtIndex(0).approximateWithValueForSymbol<float>(unknownN, unknownSymbolValue, ctx, Preferences::sharedPreferences()->complexFormat(),Preferences::sharedPreferences()->angleUnit());
-  if (std::floor(rank) == rank) {
+  if (std::floor(rank) == rank && seq.hasValidExpression()) {
     SequenceContext sqctx(ctx, sequenceStore());
     return Float<double>::Builder(seq.evaluateXYAtParameter(rank, &sqctx).x2());
   } else {
diff --git a/apps/shared/sequence.h b/apps/shared/sequence.h
index 016d12e23..dffbc45b8 100644
--- a/apps/shared/sequence.h
+++ b/apps/shared/sequence.h
@@ -59,6 +59,7 @@ public:
   Poincare::Layout nameLayout();
   bool isDefined() override;
   bool isEmpty() override;
+  bool hasValidExpression() { return m_definition.hasValidExpression(); }
   // Approximation
   Poincare::Coordinate2D<float> evaluateXYAtParameter(float x, Poincare::Context * context) const override {
     return Poincare::Coordinate2D<float>(x, templatedApproximateAtAbscissa(x, static_cast<SequenceContext *>(context)));
diff --git a/apps/shared/sequence_context.cpp b/apps/shared/sequence_context.cpp
index fc1f48738..528a2c359 100644
--- a/apps/shared/sequence_context.cpp
+++ b/apps/shared/sequence_context.cpp
@@ -87,9 +87,14 @@ void TemplatedSequenceContext<T>::step(SequenceContext * sqctx, int sequenceInde
   SequenceStore * sequenceStore = sqctx->sequenceStore();
   stop = stepMultipleSequences ? sequenceStore->numberOfModels() : start + 1;
   for (int i = start; i < stop; i++) {
-    Sequence * u = sequenceStore->modelForRecord(sequenceStore->recordAtIndex(i));
-    int index = stepMultipleSequences ? SequenceStore::sequenceIndexForName(u->fullName()[0]) : 0;
-    sequences[index] = u->isDefined() ? u : nullptr;
+    Ion::Storage::Record record = sequenceStore->recordAtIndex(i);
+    if (!record.isNull()) {
+      Sequence * u = sequenceStore->modelForRecord(record);
+      int index = stepMultipleSequences ? SequenceStore::sequenceIndexForName(u->fullName()[0]) : 0;
+      sequences[index] = u->isDefined() ? u : nullptr;
+    } else {
+      sequences[i] = nullptr;
+    }
   }
 
   // We approximate the value of the next rank for each sequence we want to update