diff --git a/poincare/src/binomial_coefficient.cpp b/poincare/src/binomial_coefficient.cpp
index be7a18477..343de9a9e 100644
--- a/poincare/src/binomial_coefficient.cpp
+++ b/poincare/src/binomial_coefficient.cpp
@@ -65,7 +65,9 @@ Expression BinomialCoefficient::shallowReduce(Context * context) {
   Expression c1 = childAtIndex(1);
 
   if (SortedIsMatrix(c0, context) || SortedIsMatrix(c1, context)) {
-    return Undefined::Builder();
+    Expression result = Undefined::Builder();
+    replaceWithInPlace(result);
+    return result;
   }
 
   if (c0.type() == ExpressionNode::Type::Rational) {
diff --git a/poincare/src/confidence_interval.cpp b/poincare/src/confidence_interval.cpp
index b9780e78e..db026ccd6 100644
--- a/poincare/src/confidence_interval.cpp
+++ b/poincare/src/confidence_interval.cpp
@@ -62,7 +62,9 @@ Expression ConfidenceInterval::shallowReduce(ExpressionNode::ReductionContext re
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (SortedIsMatrix(c0, reductionContext.context()) || SortedIsMatrix(c1, reductionContext.context())) {
-    return Undefined::Builder();
+    Expression result = Undefined::Builder();
+    replaceWithInPlace(result);
+    return result;
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational&>(c0);
diff --git a/poincare/src/derivative.cpp b/poincare/src/derivative.cpp
index d37027df3..52cb396ce 100644
--- a/poincare/src/derivative.cpp
+++ b/poincare/src/derivative.cpp
@@ -146,7 +146,9 @@ Expression Derivative::shallowReduce(Context * context) {
       || SortedIsMatrix(childAtIndex(1), context)
       || SortedIsMatrix(childAtIndex(2), context))
   {
-    return Undefined::Builder();
+    Expression result = Undefined::Builder();
+    replaceWithInPlace(result);
+    return result;
   }
   // TODO: to be implemented diff(+) -> +diff() etc
   return *this;
diff --git a/poincare/src/integral.cpp b/poincare/src/integral.cpp
index 03efa8741..6542fe855 100644
--- a/poincare/src/integral.cpp
+++ b/poincare/src/integral.cpp
@@ -225,7 +225,9 @@ Expression Integral::shallowReduce(Context * context) {
       || SortedIsMatrix(childAtIndex(2), context)
       || SortedIsMatrix(childAtIndex(3), context))
   {
-    return Undefined::Builder();
+    Expression result = Undefined::Builder();
+    replaceWithInPlace(result);
+    return result;
   }
   return *this;
 }