diff --git a/poincare/include/poincare/division.h b/poincare/include/poincare/division.h
index 602f1184d..4b924844d 100644
--- a/poincare/include/poincare/division.h
+++ b/poincare/include/poincare/division.h
@@ -25,7 +25,7 @@ public:
   // Properties
   Type type() const override { return Type::Division; }
   int polynomialDegree(Context * context, const char * symbolName) const override;
-  Expression extractUnits() override { assert(false); return ExpressionNode::extractUnits(); }
+  Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
 
   // Approximation
   virtual Evaluation<float> approximate(SinglePrecision p, Context * context, Preferences::ComplexFormat complexFormat, Preferences::AngleUnit angleUnit) const override {
diff --git a/poincare/include/poincare/empty_expression.h b/poincare/include/poincare/empty_expression.h
index 3a64cac18..0ac5a21e7 100644
--- a/poincare/include/poincare/empty_expression.h
+++ b/poincare/include/poincare/empty_expression.h
@@ -22,7 +22,7 @@ public:
   // Properties
   Type type() const override { return Type::EmptyExpression; }
   int serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
-  Expression extractUnits() override { assert(false); return ExpressionNode::extractUnits(); }
+  Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
 
   // Simplification
   LayoutShape leftLayoutShape() const override {
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index c25545bca..323804f15 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -199,7 +199,7 @@ public:
   Expression replaceSymbolWithExpression(const SymbolAbstract & symbol, const Expression & expression) { return node()->replaceSymbolWithExpression(symbol, expression); }
 
   /* Units */
-  Expression extractUnits() { return node()->extractUnits(); }
+  Expression removeUnit(Expression * unit) { return node()->removeUnit(unit); }
   bool hasUnit() const;
 
   /* Complex */
diff --git a/poincare/include/poincare/expression_node.h b/poincare/include/poincare/expression_node.h
index 896a72c28..1a06b3b6e 100644
--- a/poincare/include/poincare/expression_node.h
+++ b/poincare/include/poincare/expression_node.h
@@ -178,7 +178,7 @@ public:
   virtual float characteristicXRange(Context * context, Preferences::AngleUnit angleUnit) const;
   bool isOfType(Type * types, int length) const;
 
-  virtual Expression extractUnits(); // Only reduced nodes should answer
+  virtual Expression removeUnit(Expression * unit); // Only reduced nodes should answer
 
   /* Simplification */
   /* SimplificationOrder returns:
diff --git a/poincare/include/poincare/multiplication.h b/poincare/include/poincare/multiplication.h
index 46dfea69f..4b1c41a74 100644
--- a/poincare/include/poincare/multiplication.h
+++ b/poincare/include/poincare/multiplication.h
@@ -25,7 +25,7 @@ public:
   int polynomialDegree(Context * context, const char * symbolName) const override;
   int getPolynomialCoefficients(Context * context, const char * symbolName, Expression coefficients[], ExpressionNode::SymbolicComputation symbolicComputation) const override;
   bool childAtIndexNeedsUserParentheses(const Expression & child, int childIndex) const override;
-  Expression extractUnits() override;
+  Expression removeUnit(Expression * unit) override;
 
   // Approximation
   template<typename T> static Complex<T> compute(const std::complex<T> c, const std::complex<T> d, Preferences::ComplexFormat complexFormat) { return Complex<T>::Builder(c*d); }
@@ -65,6 +65,7 @@ private:
 class Multiplication : public NAryExpression {
   friend class Addition;
   friend class Power;
+  friend class MultiplicationNode;
 public:
   Multiplication(const MultiplicationNode * n) : NAryExpression(n) {}
   static Multiplication Builder(const Tuple & children = {}) { return TreeHandle::NAryBuilder<Multiplication, MultiplicationNode>(convert(children)); }
@@ -76,7 +77,7 @@ public:
 
   // Properties
   int getPolynomialCoefficients(Context * context, const char * symbolName, Expression coefficients[], ExpressionNode::SymbolicComputation symbolicComputation) const;
-  Expression extractUnits();
+
   // Approximation
   template<typename T> static void computeOnArrays(T * m, T * n, T * result, int mNumberOfColumns, int mNumberOfRows, int nNumberOfColumns);
   // Simplification
@@ -88,6 +89,9 @@ public:
     NAryExpression::sortChildrenInPlace(order, context, false, canBeInterrupted);
   }
 private:
+  // Unit
+  Expression removeUnit(Expression * unit);
+
   // Simplification
   Expression privateShallowReduce(ExpressionNode::ReductionContext reductionContext, bool expand, bool canBeInterrupted);
   void factorizeBase(int i, int j, ExpressionNode::ReductionContext reductionContext);
diff --git a/poincare/include/poincare/nth_root.h b/poincare/include/poincare/nth_root.h
index 5132282f6..b1280494a 100644
--- a/poincare/include/poincare/nth_root.h
+++ b/poincare/include/poincare/nth_root.h
@@ -20,7 +20,7 @@ public:
 #endif
 
 private:
-  Expression extractUnits() override { assert(false); return ExpressionNode::extractUnits(); }
+  Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
   // Layout
   Layout createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
   int serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
diff --git a/poincare/include/poincare/parenthesis.h b/poincare/include/poincare/parenthesis.h
index 682c7630a..66fe39ca2 100644
--- a/poincare/include/poincare/parenthesis.h
+++ b/poincare/include/poincare/parenthesis.h
@@ -21,7 +21,7 @@ public:
   // Properties
   Type type() const override { return Type::Parenthesis; }
   int polynomialDegree(Context * context, const char * symbolName) const override;
-  Expression extractUnits() override { assert(false); return ExpressionNode::extractUnits(); }
+  Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
 
   // Layout
   Layout createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
diff --git a/poincare/include/poincare/power.h b/poincare/include/poincare/power.h
index d9da121c7..815dc065c 100644
--- a/poincare/include/poincare/power.h
+++ b/poincare/include/poincare/power.h
@@ -29,7 +29,7 @@ public:
   Sign sign(Context * context) const override;
   Expression setSign(Sign s, ReductionContext reductionContext) override;
   bool childAtIndexNeedsUserParentheses(const Expression & child, int childIndex) const override;
-  Expression extractUnits() override;
+  Expression removeUnit(Expression * unit) override;
 
   int polynomialDegree(Context * context, const char * symbolName) const override;
   int getPolynomialCoefficients(Context * context, const char * symbolName, Expression coefficients[], ExpressionNode::SymbolicComputation symbolicComputation) const override;
@@ -84,6 +84,9 @@ private:
   constexpr static int k_maxExactPowerMatrix = 100;
   constexpr static int k_maxNumberOfTermsInExpandedMultinome = 25;
 
+  // Unit
+  Expression removeUnit(Expression * unit);
+
   // Simplification
   Expression denominator(ExpressionNode::ReductionContext reductionContext) const;
 
diff --git a/poincare/include/poincare/subtraction.h b/poincare/include/poincare/subtraction.h
index 96db82b72..92e213ba9 100644
--- a/poincare/include/poincare/subtraction.h
+++ b/poincare/include/poincare/subtraction.h
@@ -24,7 +24,7 @@ public:
   Type type() const override { return Type::Subtraction; }
   int polynomialDegree(Context * context, const char * symbolName) const override;
   bool childAtIndexNeedsUserParentheses(const Expression & child, int childIndex) const override;
-  Expression extractUnits() override { assert(false); return ExpressionNode::extractUnits(); }
+  Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
 
   // Approximation
   template<typename T> static Complex<T> compute(const std::complex<T> c, const std::complex<T> d, Preferences::ComplexFormat complexFormat) { return Complex<T>::Builder(c - d); }
diff --git a/poincare/include/poincare/unit.h b/poincare/include/poincare/unit.h
index 1b809fab3..6f5596cec 100644
--- a/poincare/include/poincare/unit.h
+++ b/poincare/include/poincare/unit.h
@@ -151,7 +151,7 @@ public:
   // Expression Properties
   Type type() const override { return Type::Unit; }
   Sign sign(Context * context) const override;
-  Expression extractUnits() override;
+  Expression removeUnit(Expression * unit) override;
 
   /* Layout */
   Layout createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
@@ -183,6 +183,7 @@ private:
 };
 
 class Unit final : public Expression {
+  friend class UnitNode;
 public:
   typedef UnitNode::Prefix Prefix;
   typedef UnitNode::Representative Representative;
@@ -728,6 +729,9 @@ public:
   // Simplification
   Expression shallowReduce(ExpressionNode::ReductionContext reductionContext);
   void chooseBestMultipleForValue(double & value, const int exponent, ExpressionNode::ReductionContext reductionContext);
+
+private:
+  Expression removeUnit(Expression * unit);
 };
 
 }
diff --git a/poincare/include/poincare/unit_convert.h b/poincare/include/poincare/unit_convert.h
index c142cb712..b1ff98b1d 100644
--- a/poincare/include/poincare/unit_convert.h
+++ b/poincare/include/poincare/unit_convert.h
@@ -20,7 +20,7 @@ public:
   Type type() const override { return Type::UnitConvert; }
 
 private:
-  Expression extractUnits() override { assert(false); return ExpressionNode::extractUnits(); }
+  Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
   // Simplification
   Expression shallowReduce(ReductionContext reductionContext) override;
   // Evalutation
diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index 4bdec595a..076c054b7 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -155,10 +155,12 @@ Expression Addition::shallowReduce(ExpressionNode::ReductionContext reductionCon
   /* Step 2: Handle the units. All children should have the same unit, otherwise
    * the result is not homogeneous. */
   {
-    Expression unit = childAtIndex(0).extractUnits();
+    Expression unit;
+    childAtIndex(0).removeUnit(&unit);
     const bool hasUnit = !unit.isUninitialized();
     for (int i = 1; i < childrenCount; i++) {
-      Expression otherUnit = childAtIndex(i).extractUnits();
+      Expression otherUnit;
+      childAtIndex(i).removeUnit(&otherUnit);
       if (hasUnit == otherUnit.isUninitialized() ||
           (hasUnit && !unit.isIdenticalTo(otherUnit)))
       {
@@ -166,15 +168,6 @@ Expression Addition::shallowReduce(ExpressionNode::ReductionContext reductionCon
       }
     }
     if (hasUnit) {
-      for (int i = 0; i < childrenCount; i++) {
-        /* Any unary hierarchy must be squashed here since it has not been
-         * done in extractUnits.
-         */
-        Expression child = childAtIndex(i);
-        if (child.type() == ExpressionNode::Type::Multiplication) {
-          static_cast<Multiplication &>(child).squashUnaryHierarchyInPlace();
-        }
-      }
       Expression addition = shallowReduce(reductionContext);
       Multiplication result = Multiplication::Builder(unit);
       result.mergeSameTypeChildrenInPlace();
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index 40329a08e..119574427 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -350,7 +350,9 @@ Expression Expression::defaultHandleUnitsInChildren() {
   // Generically, an Expression does not accept any Unit in its children.
   const int childrenCount = numberOfChildren();
   for (int i = 0; i < childrenCount; i++) {
-    if (!childAtIndex(i).extractUnits().isUninitialized()) {
+    Expression unit;
+    childAtIndex(i).removeUnit(&unit);
+    if (!unit.isUninitialized()) {
       return replaceWithUndefinedInPlace();
     }
   }
diff --git a/poincare/src/expression_node.cpp b/poincare/src/expression_node.cpp
index dc87f141f..fe117da7e 100644
--- a/poincare/src/expression_node.cpp
+++ b/poincare/src/expression_node.cpp
@@ -136,8 +136,8 @@ bool ExpressionNode::isOfType(Type * types, int length) const {
   return false;
 }
 
-Expression ExpressionNode::extractUnits() {
-  return Expression();
+Expression ExpressionNode::removeUnit(Expression * unit) {
+  return Expression(this);
 }
 
 void ExpressionNode::setChildrenInPlace(Expression other) {
diff --git a/poincare/src/multiplication.cpp b/poincare/src/multiplication.cpp
index 85b00d24a..d3b6391ee 100644
--- a/poincare/src/multiplication.cpp
+++ b/poincare/src/multiplication.cpp
@@ -63,8 +63,8 @@ bool MultiplicationNode::childAtIndexNeedsUserParentheses(const Expression & chi
   return child.isOfType(types, 2);
 }
 
-Expression MultiplicationNode::extractUnits() {
-  return Multiplication(this).extractUnits();
+Expression MultiplicationNode::removeUnit(Expression * unit) {
+  return Multiplication(this).removeUnit(unit);
 }
 
 template<typename T>
@@ -255,31 +255,30 @@ int Multiplication::getPolynomialCoefficients(Context * context, const char * sy
   return deg;
 }
 
-Expression Multiplication::extractUnits() {
-  Multiplication result = Multiplication::Builder();
+Expression Multiplication::removeUnit(Expression * unit) {
+  Multiplication unitMult = Multiplication::Builder();
   int resultChildrenCount = 0;
   for (int i = 0; i < numberOfChildren(); i++) {
-    Expression currentUnit = childAtIndex(i).extractUnits();
+    Expression currentUnit;
+    childAtIndex(i).removeUnit(&currentUnit);
     if (!currentUnit.isUninitialized()) {
-      assert(childAtIndex(i) == currentUnit);
-      result.addChildAtIndexInPlace(currentUnit, resultChildrenCount, resultChildrenCount);
+      unitMult.addChildAtIndexInPlace(currentUnit, resultChildrenCount, resultChildrenCount);
       resultChildrenCount++;
+      assert(childAtIndex(i).isRationalOne());
       removeChildAtIndexInPlace(i--);
     }
   }
   if (resultChildrenCount == 0) {
-    return Expression();
+    *unit = Expression();
+  } else {
+    *unit = unitMult.squashUnaryHierarchyInPlace();
   }
-  /* squashUnaryHierarchyInPlace();
-   * That would make 'this' invalid, so we would rather keep any unary
-   * hierarchy as it is and handle it later.
-   * TODO ?
-   * A possible solution would be that the extractUnits method becomes
-   *   Expression extractUnits(Expression & units)
-   * returning the Expression that is left after extracting the units
-   * and setting the units reference instead of returning the units.
-   */
-  return result.squashUnaryHierarchyInPlace();
+  if (numberOfChildren() == 0) {
+    Expression one = Rational::Builder(1);
+    replaceWithInPlace(one);
+    return one;
+  }
+  return squashUnaryHierarchyInPlace();
 }
 
 template<typename T>
@@ -356,9 +355,11 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
     return std::move(o);
   }
 
-  Expression result = *this;
-  Expression units = extractUnits();
+  Expression self = *this;
+  Expression units;
+  self = removeUnit(&units);
 
+  Expression result;
   if (!units.isUninitialized()) {
     /* Step 2: Handle the units
      *
@@ -408,8 +409,12 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
     }
     if (unitsAccu.numberOfChildren() > 0) {
       units = Division::Builder(units, unitsAccu.clone()).deepReduce(reductionContext);
-      Expression newUnits = units.extractUnits();
-      result = Multiplication::Builder(result, units);
+      Expression newUnits;
+      units = units.removeUnit(&newUnits);
+      Multiplication m = Multiplication::Builder(units);
+      self.replaceWithInPlace(m);
+      m.addChildAtIndexInPlace(self, 0, 1);
+      self = m;
       if (newUnits.isUninitialized()) {
         units = unitsAccu;
       } else {
@@ -426,7 +431,7 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
      * most relevant.
      */
 
-    double value = result.approximateToScalar<double>(reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
+    double value = self.approximateToScalar<double>(reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
     if (std::isnan(value)) {
       // If the value is undefined, return "undef" without any unit
       result = Undefined::Builder();
@@ -480,7 +485,7 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
     }
   }
 
-  replaceWithInPlace(result);
+  self.replaceWithInPlace(result);
   return result;
 }
 
@@ -1006,7 +1011,7 @@ bool Multiplication::TermHasNumeralExponent(const Expression & e) {
 }
 
 void Multiplication::splitIntoNormalForm(Expression & numerator, Expression & denominator, ExpressionNode::ReductionContext reductionContext) const {
-  assert(const_cast<Multiplication*>(this)->extractUnits().isUninitialized());
+  assert(!hasUnit());
   Multiplication mNumerator = Multiplication::Builder();
   Multiplication mDenominator = Multiplication::Builder();
   int numberOfFactorsInNumerator = 0;
diff --git a/poincare/src/power.cpp b/poincare/src/power.cpp
index 9d9ee0a62..8f5729bc2 100644
--- a/poincare/src/power.cpp
+++ b/poincare/src/power.cpp
@@ -81,12 +81,8 @@ int PowerNode::polynomialDegree(Context * context, const char * symbolName) cons
   return -1;
 }
 
-Expression PowerNode::extractUnits() {
-  if (!childAtIndex(0)->extractUnits().isUninitialized()) {
-    assert(childAtIndex(0)->type() == ExpressionNode::Type::Unit);
-    return Power(this);
-  }
-  return ExpressionNode::extractUnits();
+Expression PowerNode::removeUnit(Expression * unit) {
+  return Power(this).removeUnit(unit);
 }
 
 int PowerNode::getPolynomialCoefficients(Context * context, const char * symbolName, Expression coefficients[], ExpressionNode::SymbolicComputation symbolicComputation) const {
@@ -378,6 +374,23 @@ int Power::getPolynomialCoefficients(Context * context, const char * symbolName,
   return -1;
 }
 
+Expression Power::removeUnit(Expression * unit) {
+  Expression childUnit;
+  Expression child = childAtIndex(0).node()->removeUnit(&childUnit);
+  if (!childUnit.isUninitialized()) {
+    // Reduced power containing unit are of form "unit^i" with i integer
+    assert(child.isRationalOne());
+    assert(childUnit.type() == ExpressionNode::Type::Unit);
+    Power p = *this;
+    Expression result = child;
+    replaceWithInPlace(child);
+    p.replaceChildAtIndexInPlace(0, childUnit);
+    *unit = p;
+    return child;
+  }
+  return *this;
+}
+
 Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContext) {
 
   {
@@ -392,10 +405,13 @@ Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContex
 
   // Step 1: Handle the units
   {
-    if (!index.extractUnits().isUninitialized()) {
+    Expression indexUnit;
+    index.removeUnit(&indexUnit);
+    if (!indexUnit.isUninitialized()) {
       // There must be no unit in the exponent
       return replaceWithUndefinedInPlace();
     }
+    assert(index == childAtIndex(1));
     if (base.hasUnit()) {
       if (index.type() != ExpressionNode::Type::Rational || !static_cast<Rational &>(index).isInteger()) {
         // The exponent must be an Integer
diff --git a/poincare/src/unit.cpp b/poincare/src/unit.cpp
index dfe857004..8501d3e0a 100644
--- a/poincare/src/unit.cpp
+++ b/poincare/src/unit.cpp
@@ -164,8 +164,8 @@ ExpressionNode::Sign UnitNode::sign(Context * context) const {
   return Sign::Positive;
 }
 
-Expression UnitNode::extractUnits() {
-  return Unit(this);
+Expression UnitNode::removeUnit(Expression * unit) {
+  return Unit(this).removeUnit(unit);
 }
 
 int UnitNode::simplificationOrderSameType(const ExpressionNode * e, bool ascending, bool canBeInterrupted, bool ignoreParentheses) const {
@@ -341,6 +341,13 @@ void Unit::chooseBestMultipleForValue(double & value, const int exponent, Expres
   value = bestVal;
 }
 
+Expression Unit::removeUnit(Expression * unit) {
+  *unit = *this;
+  Expression one = Rational::Builder(1);
+  replaceWithInPlace(one);
+  return one;
+}
+
 template Evaluation<float> UnitNode::templatedApproximate<float>(Context * context, Preferences::ComplexFormat complexFormat, Preferences::AngleUnit angleUnit) const;
 template Evaluation<double> UnitNode::templatedApproximate<double>(Context * context, Preferences::ComplexFormat complexFormat, Preferences::AngleUnit angleUnit) const;
 
diff --git a/poincare/src/unit_convert.cpp b/poincare/src/unit_convert.cpp
index 148897ef5..2ca423e48 100644
--- a/poincare/src/unit_convert.cpp
+++ b/poincare/src/unit_convert.cpp
@@ -41,7 +41,8 @@ Expression UnitConvert::shallowReduce(ExpressionNode::ReductionContext reduction
         reductionContext.angleUnit(),
         reductionContext.target(),
         ExpressionNode::SymbolicComputation::ReplaceAllSymbolsWithUndefinedAndReplaceUnits);
-    Expression unit = childAtIndex(1).clone().reduce(reductionContextWithUnits).extractUnits();
+    Expression unit;
+    childAtIndex(1).clone().reduce(reductionContextWithUnits).removeUnit(&unit);
     if (unit.isUninitialized()) {
       // There is no unit on the right
       return replaceWithUndefinedInPlace();
@@ -54,18 +55,21 @@ Expression UnitConvert::shallowReduce(ExpressionNode::ReductionContext reduction
       reductionContext.angleUnit(),
       reductionContext.target(),
       ExpressionNode::SymbolicComputation::ReplaceAllSymbolsWithUndefinedAndDoNotReplaceUnits);
-  Expression finalUnit = childAtIndex(1).reduce(reductionContextWithoutUnits).extractUnits();
+  Expression finalUnit;
+  childAtIndex(1).reduce(reductionContextWithoutUnits).removeUnit(&finalUnit);
 
   // Divide the left member by the new unit
   Expression division = Division::Builder(childAtIndex(0), finalUnit.clone());
   division = division.reduce(reductionContext);
-  if (!division.extractUnits().isUninitialized()) {
+  Expression divisionUnit;
+  division = division.removeUnit(&divisionUnit);
+  if (!divisionUnit.isUninitialized()) {
     // The left and right members are not homogeneous
     return replaceWithUndefinedInPlace();
   }
   double floatValue = division.approximateToScalar<double>(reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
   if (std::isinf(floatValue)) {
-    return Infinity::Builder(false); //FIXME sign?
+    return Infinity::Builder(floatValue < 0.0); //FIXME sign?
   }
   if (std::isnan(floatValue)) {
     return Undefined::Builder();
diff --git a/poincare/test/expression_properties.cpp b/poincare/test/expression_properties.cpp
index c5d9ee0c4..5d03ca620 100644
--- a/poincare/test/expression_properties.cpp
+++ b/poincare/test/expression_properties.cpp
@@ -373,10 +373,12 @@ void assert_reduced_expression_unit(const char * expression, const char * unit,
   ExpressionNode::ReductionContext redContext(&globalContext, Real, Degree, SystemForApproximation, symbolicComutation);
   Expression e = parse_expression(expression, &globalContext, false);
   e = e.reduce(redContext);
-  Expression u1 = e.extractUnits();
-  Expression u2 = parse_expression(unit, &globalContext, false);
-  u2 = u2.reduce(redContext);
-  u2 = u2.extractUnits();
+  Expression u1;
+  e = e.removeUnit(&u1);
+  Expression e2 = parse_expression(unit, &globalContext, false);
+  Expression u2;
+  e2 = e2.reduce(redContext);
+  e2.removeUnit(&u2);
   quiz_assert_print_if_failure(u1.isUninitialized() == u2.isUninitialized() && (u1.isUninitialized() || u1.isIdenticalTo(u2)), expression);
 }