diff --git a/poincare/include/poincare/absolute_value.h b/poincare/include/poincare/absolute_value.h
index bdbfc37d5..6e841e7a7 100644
--- a/poincare/include/poincare/absolute_value.h
+++ b/poincare/include/poincare/absolute_value.h
@@ -21,6 +21,7 @@ public:
   // Properties
   Type type() const override { return Type::AbsoluteValue; }
   Sign sign(Context * context) const override { return Sign::Positive; }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Expression setSign(Sign s, ReductionContext reductionContext) override;
 
   // Approximation
diff --git a/poincare/include/poincare/arc_cosine.h b/poincare/include/poincare/arc_cosine.h
index 43bac523f..389ac4c79 100644
--- a/poincare/include/poincare/arc_cosine.h
+++ b/poincare/include/poincare/arc_cosine.h
@@ -20,6 +20,7 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context) == Sign::Unknown ? Sign::Unknown : Sign::Positive; }
   Type type() const override { return Type::ArcCosine; }
 
 private:
diff --git a/poincare/include/poincare/arc_sine.h b/poincare/include/poincare/arc_sine.h
index 2747bda13..a567d55a1 100644
--- a/poincare/include/poincare/arc_sine.h
+++ b/poincare/include/poincare/arc_sine.h
@@ -20,6 +20,8 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Type type() const override { return Type::ArcSine; }
 private:
   // Layout
diff --git a/poincare/include/poincare/arc_tangent.h b/poincare/include/poincare/arc_tangent.h
index 47b6f5638..44c0ff887 100644
--- a/poincare/include/poincare/arc_tangent.h
+++ b/poincare/include/poincare/arc_tangent.h
@@ -20,6 +20,8 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Type type() const override { return Type::ArcTangent; }
 
 private:
diff --git a/poincare/include/poincare/ceiling.h b/poincare/include/poincare/ceiling.h
index ff1bc5a10..a85897706 100644
--- a/poincare/include/poincare/ceiling.h
+++ b/poincare/include/poincare/ceiling.h
@@ -19,6 +19,7 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
   Type type() const override { return Type::Ceiling; }
 private:
   // Layout
diff --git a/poincare/include/poincare/complex_cartesian.h b/poincare/include/poincare/complex_cartesian.h
index f9a71c5fd..7d9730482 100644
--- a/poincare/include/poincare/complex_cartesian.h
+++ b/poincare/include/poincare/complex_cartesian.h
@@ -19,6 +19,8 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(1)->nullStatus(context) == NullStatus::Null ? childAtIndex(0)->sign(context) : Sign::Unknown; }
+  NullStatus nullStatus(Context * context) const override;
   Type type() const override { return Type::ComplexCartesian; }
 private:
   // Layout
diff --git a/poincare/include/poincare/conjugate.h b/poincare/include/poincare/conjugate.h
index 61b442fc5..e2f90f170 100644
--- a/poincare/include/poincare/conjugate.h
+++ b/poincare/include/poincare/conjugate.h
@@ -19,6 +19,8 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Type type() const override { return Type::Conjugate; }
 private:
   // Layout
diff --git a/poincare/include/poincare/division_remainder.h b/poincare/include/poincare/division_remainder.h
index 3794c370d..e8262c7a2 100644
--- a/poincare/include/poincare/division_remainder.h
+++ b/poincare/include/poincare/division_remainder.h
@@ -20,6 +20,7 @@ public:
 #endif
 
   // ExpressionNode
+  Sign sign(Context * context) const override { return Sign::Positive; }
   Type type() const override { return Type::DivisionRemainder; }
 
 
diff --git a/poincare/include/poincare/factor.h b/poincare/include/poincare/factor.h
index 39e1ce4d5..329fe1902 100644
--- a/poincare/include/poincare/factor.h
+++ b/poincare/include/poincare/factor.h
@@ -18,6 +18,8 @@ public:
     stream << "Factor";
   }
 #endif
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Type type() const override { return Type::Factor; }
 private:
   /* Layout */
diff --git a/poincare/include/poincare/factorial.h b/poincare/include/poincare/factorial.h
index 212a94c57..2f39b2062 100644
--- a/poincare/include/poincare/factorial.h
+++ b/poincare/include/poincare/factorial.h
@@ -19,6 +19,7 @@ public:
 #endif
 
   // Properties
+  NullStatus nullStatus(Context * context) const override { return NullStatus::NonNull; }
   Type type() const override { return Type::Factorial; }
   Sign sign(Context * context) const override { return Sign::Positive; }
   Expression setSign(Sign s, ReductionContext reductionContext) override;
diff --git a/poincare/include/poincare/floor.h b/poincare/include/poincare/floor.h
index 65115adaa..5d360389f 100644
--- a/poincare/include/poincare/floor.h
+++ b/poincare/include/poincare/floor.h
@@ -19,6 +19,7 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
   Type type() const override { return Type::Floor; }
 
 private:
diff --git a/poincare/include/poincare/frac_part.h b/poincare/include/poincare/frac_part.h
index 0158bb9e7..54e95817e 100644
--- a/poincare/include/poincare/frac_part.h
+++ b/poincare/include/poincare/frac_part.h
@@ -19,10 +19,9 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return Sign::Positive; }
   Type type() const override { return Type::FracPart; }
 
-
-
 private:
   // Layout
   Layout createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
diff --git a/poincare/include/poincare/great_common_divisor.h b/poincare/include/poincare/great_common_divisor.h
index d5a6c4ae3..09ef262ba 100644
--- a/poincare/include/poincare/great_common_divisor.h
+++ b/poincare/include/poincare/great_common_divisor.h
@@ -17,6 +17,7 @@ public:
 #endif
 
   // ExpressionNode
+  Sign sign(Context * context) const override { return Sign::Positive; }
   Type type() const override { return Type::GreatCommonDivisor; }
 
 private:
diff --git a/poincare/include/poincare/imaginary_part.h b/poincare/include/poincare/imaginary_part.h
index 345ddbc50..6fd7209ff 100644
--- a/poincare/include/poincare/imaginary_part.h
+++ b/poincare/include/poincare/imaginary_part.h
@@ -19,9 +19,9 @@ public:
 #endif
 
   // Properties
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->sign(context) != Sign::Unknown ? NullStatus::Null : NullStatus::Unknown; }
   Type type() const override { return Type::ImaginaryPart; }
 
-
 private:
   // Layout
   Layout createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
diff --git a/poincare/include/poincare/least_common_multiple.h b/poincare/include/poincare/least_common_multiple.h
index 1feda8cb7..fe0e15a8e 100644
--- a/poincare/include/poincare/least_common_multiple.h
+++ b/poincare/include/poincare/least_common_multiple.h
@@ -17,6 +17,7 @@ public:
 #endif
 
   // ExpressionNode
+  Sign sign(Context * context) const override { return Sign::Positive; }
   Type type() const override { return Type::LeastCommonMultiple; }
 
 private:
diff --git a/poincare/include/poincare/opposite.h b/poincare/include/poincare/opposite.h
index c4fc89166..de8e0996f 100644
--- a/poincare/include/poincare/opposite.h
+++ b/poincare/include/poincare/opposite.h
@@ -23,6 +23,7 @@ public:
 #endif
 
   // Properties
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Type type() const override { return Type::Opposite; }
   int polynomialDegree(Context * context, const char * symbolName) const override;
   Sign sign(Context * context) const override;
diff --git a/poincare/include/poincare/parenthesis.h b/poincare/include/poincare/parenthesis.h
index 66fe39ca2..bf1fcae89 100644
--- a/poincare/include/poincare/parenthesis.h
+++ b/poincare/include/poincare/parenthesis.h
@@ -19,6 +19,8 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Type type() const override { return Type::Parenthesis; }
   int polynomialDegree(Context * context, const char * symbolName) const override;
   Expression removeUnit(Expression * unit) override { assert(false); return ExpressionNode::removeUnit(unit); }
diff --git a/poincare/include/poincare/permute_coefficient.h b/poincare/include/poincare/permute_coefficient.h
index 1bc05924b..5ebfb0032 100644
--- a/poincare/include/poincare/permute_coefficient.h
+++ b/poincare/include/poincare/permute_coefficient.h
@@ -22,7 +22,7 @@ public:
 
   // Properties
   Type type() const override{ return Type::PermuteCoefficient; }
-
+  Sign sign(Context * context) const override { return Sign::Positive; }
 
 private:
   // Layout
diff --git a/poincare/include/poincare/real_part.h b/poincare/include/poincare/real_part.h
index ddcbd24a7..a35db4b94 100644
--- a/poincare/include/poincare/real_part.h
+++ b/poincare/include/poincare/real_part.h
@@ -19,6 +19,8 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context) == NullStatus::Null ? NullStatus::Null : NullStatus::Unknown; }
   Type type() const override { return Type::RealPart; }
 
 
diff --git a/poincare/include/poincare/round.h b/poincare/include/poincare/round.h
index bb4a769aa..1d4ec886b 100644
--- a/poincare/include/poincare/round.h
+++ b/poincare/include/poincare/round.h
@@ -20,6 +20,7 @@ public:
 
 
   // Properties
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
   Type type() const override { return Type::Round; }
 private:
   // Layout
diff --git a/poincare/include/poincare/sign_function.h b/poincare/include/poincare/sign_function.h
index d5379058a..dbb590c35 100644
--- a/poincare/include/poincare/sign_function.h
+++ b/poincare/include/poincare/sign_function.h
@@ -20,7 +20,8 @@ public:
 
   // Properties
   Type type() const override { return Type::SignFunction; }
-  Sign sign(Context * context) const override;
+  Sign sign(Context * context) const override { return childAtIndex(0)->sign(context); }
+  NullStatus nullStatus(Context * context) const override { return childAtIndex(0)->nullStatus(context); }
   Expression setSign(Sign s, ReductionContext reductionContext) override;
 
 
diff --git a/poincare/include/poincare/unit.h b/poincare/include/poincare/unit.h
index c44138a41..2437e83d4 100644
--- a/poincare/include/poincare/unit.h
+++ b/poincare/include/poincare/unit.h
@@ -456,7 +456,8 @@ public:
 
   // Expression Properties
   Type type() const override { return Type::Unit; }
-  Sign sign(Context * context) const override;
+  Sign sign(Context * context) const override { return Sign::Positive; }
+  NullStatus nullStatus(Context * context) const override { return NullStatus::NonNull; }
   Expression removeUnit(Expression * unit) override;
 
   /* Layout */
diff --git a/poincare/include/poincare/vector_norm.h b/poincare/include/poincare/vector_norm.h
index c13a6a1d8..3d2da252a 100644
--- a/poincare/include/poincare/vector_norm.h
+++ b/poincare/include/poincare/vector_norm.h
@@ -18,6 +18,7 @@ public:
 #endif
 
   // Properties
+  Sign sign(Context * context) const override { return Sign::Positive; }
   Type type() const override { return Type::VectorNorm; }
 private:
   // Layout
diff --git a/poincare/src/complex_cartesian.cpp b/poincare/src/complex_cartesian.cpp
index df7cea0c5..b02cd4199 100644
--- a/poincare/src/complex_cartesian.cpp
+++ b/poincare/src/complex_cartesian.cpp
@@ -19,6 +19,15 @@
 
 namespace Poincare {
 
+ExpressionNode::NullStatus ComplexCartesianNode::nullStatus(Context * context) const {
+  ExpressionNode::NullStatus realNullStatus = childAtIndex(0)->nullStatus(context);
+  ExpressionNode::NullStatus imagNullStatus = childAtIndex(1)->nullStatus(context);
+  if (realNullStatus == ExpressionNode::NullStatus::NonNull || imagNullStatus == ExpressionNode::NullStatus::NonNull) {
+    return ExpressionNode::NullStatus::NonNull;
+  }
+  return (realNullStatus == ExpressionNode::NullStatus::Null && imagNullStatus == ExpressionNode::NullStatus::Null) ? ExpressionNode::NullStatus::Null : ExpressionNode::NullStatus::Unknown;
+}
+
 Expression ComplexCartesianNode::shallowReduce(ReductionContext reductionContext) {
   return ComplexCartesian(this).shallowReduce();
 }
diff --git a/poincare/src/sign_function.cpp b/poincare/src/sign_function.cpp
index ba4765413..335c02543 100644
--- a/poincare/src/sign_function.cpp
+++ b/poincare/src/sign_function.cpp
@@ -15,10 +15,6 @@ constexpr Expression::FunctionHelper SignFunction::s_functionHelper;
 
 int SignFunctionNode::numberOfChildren() const { return SignFunction::s_functionHelper.numberOfChildren(); }
 
-ExpressionNode::Sign SignFunctionNode::sign(Context * context) const {
-  return childAtIndex(0)->sign(context);
-}
-
 Expression SignFunctionNode::setSign(Sign s, ReductionContext reductionContext) {
  assert(s == ExpressionNode::Sign::Positive || s == ExpressionNode::Sign::Negative);
   SignFunction sign(this);
diff --git a/poincare/src/unit.cpp b/poincare/src/unit.cpp
index 44649c450..d6d355da7 100644
--- a/poincare/src/unit.cpp
+++ b/poincare/src/unit.cpp
@@ -653,10 +653,6 @@ int UnitNode::SpeedRepresentative::setAdditionalExpressions(double value, Expres
 }
 
 // UnitNode
-ExpressionNode::Sign UnitNode::sign(Context * context) const {
-  return Sign::Positive;
-}
-
 Expression UnitNode::removeUnit(Expression * unit) {
   return Unit(this).removeUnit(unit);
 }
diff --git a/poincare/test/expression_properties.cpp b/poincare/test/expression_properties.cpp
index 379775b2f..2f83a5c7d 100644
--- a/poincare/test/expression_properties.cpp
+++ b/poincare/test/expression_properties.cpp
@@ -36,6 +36,19 @@ QUIZ_CASE(poincare_properties_is_number_zero) {
   quiz_assert(Symbol::Builder('a').nullStatus(&context) == ExpressionNode::NullStatus::Unknown);
   quiz_assert(Multiplication::Builder(Rational::Builder(1), Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::Unknown);
   quiz_assert(Addition::Builder(Rational::Builder(1), Rational::Builder(-1)).nullStatus(&context) == ExpressionNode::NullStatus::Unknown);
+
+  quiz_assert(AbsoluteValue::Builder(Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::Null);
+  quiz_assert(ArcSine::Builder(Rational::Builder(1,7)).nullStatus(&context) == ExpressionNode::NullStatus::NonNull);
+  quiz_assert(ComplexCartesian::Builder(Rational::Builder(0), Rational::Builder(3, 2)).nullStatus(&context) == ExpressionNode::NullStatus::NonNull);
+  quiz_assert(ComplexCartesian::Builder(Rational::Builder(0), Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::Null);
+  quiz_assert(Conjugate::Builder(ComplexCartesian::Builder(Rational::Builder(2, 3), Rational::Builder(3, 2))).nullStatus(&context) == ExpressionNode::NullStatus::NonNull);
+  quiz_assert(Factor::Builder(Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::Null);
+  quiz_assert(Factorial::Builder(Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::NonNull);
+  quiz_assert(ImaginaryPart::Builder(Rational::Builder(14)).nullStatus(&context) == ExpressionNode::NullStatus::Null);
+  quiz_assert(RealPart::Builder(Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::Null);
+  quiz_assert(Parenthesis::Builder(Rational::Builder(-7)).nullStatus(&context) == ExpressionNode::NullStatus::NonNull);
+  quiz_assert(SignFunction::Builder(Rational::Builder(0)).nullStatus(&context) == ExpressionNode::NullStatus::Null);
+  quiz_assert(Unit::Builder(Unit::k_powerRepresentatives, Unit::Prefix::EmptyPrefix()).nullStatus(&context) == ExpressionNode::NullStatus::NonNull);
 }
 
 QUIZ_CASE(poincare_properties_is_random) {
@@ -154,6 +167,31 @@ QUIZ_CASE(poincare_properties_rational_sign) {
   quiz_assert(Rational::Builder(0, 3).sign() == ExpressionNode::Sign::Positive);
 }
 
+QUIZ_CASE(poincare_properties_expression_sign) {
+  Shared::GlobalContext context;
+  quiz_assert(ArcCosine::Builder(Rational::Builder(-1,7)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(ArcCosine::Builder(Symbol::Builder('a')).sign(&context) == ExpressionNode::Sign::Unknown);
+  quiz_assert(ArcSine::Builder(Rational::Builder(-1,7)).sign(&context) == ExpressionNode::Sign::Negative);
+  quiz_assert(ArcTangent::Builder(Rational::Builder(1,7)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(Ceiling::Builder(Rational::Builder(7,3)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(Floor::Builder(Rational::Builder(7,3)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(Round::Builder(Rational::Builder(7,3), Rational::Builder(1)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(Conjugate::Builder(ComplexCartesian::Builder(Rational::Builder(2, 3), BasedInteger::Builder(0, Integer::Base::Binary))).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(DivisionRemainder::Builder(Decimal::Builder(2.0), Decimal::Builder(3.0)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(AbsoluteValue::Builder(Rational::Builder(-14)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(FracPart::Builder(Rational::Builder(-7,3)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(GreatCommonDivisor::Builder({Rational::Builder(-7),Rational::Builder(-7)}).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(LeastCommonMultiple::Builder({Rational::Builder(-7),Rational::Builder(-7)}).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(Opposite::Builder(Rational::Builder(7)).sign(&context) == ExpressionNode::Sign::Negative);
+  quiz_assert(Parenthesis::Builder(Rational::Builder(-7)).sign(&context) == ExpressionNode::Sign::Negative);
+  quiz_assert(PermuteCoefficient::Builder(Rational::Builder(7),Rational::Builder(8)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(RealPart::Builder(Rational::Builder(-7)).sign(&context) == ExpressionNode::Sign::Negative);
+  quiz_assert(SignFunction::Builder(Rational::Builder(-7)).sign(&context) == ExpressionNode::Sign::Negative);
+  quiz_assert(Unit::Builder(Unit::k_powerRepresentatives, Unit::Prefix::EmptyPrefix()).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(VectorNorm::Builder(BasedInteger::Builder(1)).sign(&context) == ExpressionNode::Sign::Positive);
+  quiz_assert(ArcSine::Builder(Floor::Builder(ArcTangent::Builder(Opposite::Builder(RealPart::Builder(ArcCosine::Builder(Constant::Builder(UCodePointGreekSmallLetterPi))))))).sign(&context) == ExpressionNode::Sign::Negative);
+}
+
 QUIZ_CASE(poincare_properties_sign) {
   assert_reduced_expression_sign("abs(-cos(2)+I)", Positive);
   assert_reduced_expression_sign("2.345ᴇ-23", Positive);