diff --git a/poincare/include/poincare/complex_argument.h b/poincare/include/poincare/complex_argument.h
index e52be7ada..4ba1b404a 100644
--- a/poincare/include/poincare/complex_argument.h
+++ b/poincare/include/poincare/complex_argument.h
@@ -53,4 +53,3 @@ public:
 }
 
 #endif
-
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 8195b1c41..bcd890b1c 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -22,6 +22,7 @@ class Expression : public TreeByReference {
   friend class Arithmetic;
   friend class BinomialCoefficient;
   friend class Ceiling;
+  friend class ComplexArgument;
   friend class CosineNode;
   friend class SineNode;
   friend class ExpressionNode;
diff --git a/poincare/src/complex_argument.cpp b/poincare/src/complex_argument.cpp
index 3864b49aa..61092442e 100644
--- a/poincare/src/complex_argument.cpp
+++ b/poincare/src/complex_argument.cpp
@@ -16,7 +16,7 @@ ComplexArgumentNode * ComplexArgumentNode::FailedAllocationStaticNode() {
 }
 
 LayoutReference ComplexArgumentNode::createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const {
-    return LayoutHelper::Prefix(ComplexArgument(this), floatDisplayMode, numberOfSignificantDigits, name());
+  return LayoutHelper::Prefix(ComplexArgument(this), floatDisplayMode, numberOfSignificantDigits, name());
 }
 
 int ComplexArgumentNode::serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const {
@@ -33,9 +33,11 @@ Complex<T> ComplexArgumentNode::computeOnComplex(const std::complex<T> c, Prefer
 }
 
 Expression ComplexArgument::shallowReduce(Context & context, Preferences::AngleUnit angleUnit) {
-  Expression e = Expression::defaultShallowReduce(context, angleUnit);
-  if (e.isUndefinedOrAllocationFailure()) {
-    return e;
+  {
+    Expression e = Expression::defaultShallowReduce(context, angleUnit);
+    if (e.isUndefinedOrAllocationFailure()) {
+      return e;
+    }
   }
 #if MATRIX_EXACT_REDUCING
   Expression c = childAtIndex(0);
diff --git a/poincare/src/confidence_interval.cpp b/poincare/src/confidence_interval.cpp
index f0c997602..35b299c2c 100644
--- a/poincare/src/confidence_interval.cpp
+++ b/poincare/src/confidence_interval.cpp
@@ -51,9 +51,11 @@ SimplePredictionIntervalNode * SimplePredictionIntervalNode::FailedAllocationSta
 }
 
 Expression ConfidenceInterval::shallowReduce(Context & context, Preferences::AngleUnit angleUnit) {
-  Expression e = Expression::defaultShallowReduce(context, angleUnit);
-  if (e.isUndefinedOrAllocationFailure()) {
-    return e;
+  {
+    Expression e = Expression::defaultShallowReduce(context, angleUnit);
+    if (e.isUndefinedOrAllocationFailure()) {
+      return e;
+    }
   }
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
@@ -65,13 +67,17 @@ Expression ConfidenceInterval::shallowReduce(Context & context, Preferences::Ang
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational&>(c0);
     if (r0.signedIntegerNumerator().isNegative() || Integer::NaturalOrder(r0.signedIntegerNumerator(), r0.integerDenominator()) > 0) {
-      return Undefined();
+      Expression result = Undefined();
+      replaceWithInPlace(result);
+      return result;
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational&>(c1);
     if (!r1.integerDenominator().isOne() || r1.signedIntegerNumerator().isNegative()) {
-      return Undefined();
+      Expression result = Undefined();
+      replaceWithInPlace(result);
+      return result;
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
@@ -82,11 +88,12 @@ Expression ConfidenceInterval::shallowReduce(Context & context, Preferences::Ang
   // Compute [r0-1/sqr(r1), r0+1/sqr(r1)]
   Expression sqr = Power(r1, Rational(-1, 2));
   Matrix matrix;
-  matrix.addChildAtIndexInPlace(Addition(r0, Multiplication(Rational(-1), sqr)), 0, 0);
+  matrix.addChildAtIndexInPlace(Addition(r0.clone(), Multiplication(Rational(-1), sqr.clone())), 0, 0);
   matrix.addChildAtIndexInPlace(Addition(r0, sqr), 1, 1);
   matrix.setDimensions(1, 2);
-  return matrix.deepReduce(context, angleUnit);
+  replaceWithInPlace(matrix);
+  Expression result = matrix.deepReduce(context, angleUnit);
+  return result;
 }
 
 }
-