diff --git a/poincare/include/poincare/unit.h b/poincare/include/poincare/unit.h
index 84931a149..689203e4a 100644
--- a/poincare/include/poincare/unit.h
+++ b/poincare/include/poincare/unit.h
@@ -38,6 +38,7 @@ public:
       m_symbol(symbol),
       m_exponent(exponent)
     {}
+    inline bool operator==(const Prefix& p) const { return m_exponent == p.m_exponent && strcmp(m_symbol, p.m_symbol) == 0; }
     const char * symbol() const { return m_symbol; }
     int8_t exponent() const { return m_exponent; }
     int serialize(char * buffer, int bufferSize) const;
diff --git a/poincare/src/unit.cpp b/poincare/src/unit.cpp
index 46302f3d3..8082cfef5 100644
--- a/poincare/src/unit.cpp
+++ b/poincare/src/unit.cpp
@@ -392,16 +392,16 @@ Expression Unit::removeUnit(Expression * unit) {
 }
 
 bool Unit::isSecond() const {
-  return node()->dimension() == TimeDimension && node()->representative() == SecondRepresentative && node()->prefix() == &EmptyPrefix;
+  return node()->dimension() == TimeDimension && node()->representative() == SecondRepresentative && *(node()->prefix()) == EmptyPrefix;
 }
 
 bool Unit::isMeter() const {
-  return node()->dimension() == DistanceDimension && node()->representative() == MeterRepresentative && node()->prefix() == &EmptyPrefix;
+  return node()->dimension() == DistanceDimension && node()->representative() == MeterRepresentative && *(node()->prefix()) == EmptyPrefix;
 }
 
 
 bool Unit::isKilogram() const {
-  return node()->dimension() == MassDimension && node()->representative() == KilogramRepresentative && node()->prefix() == &KiloPrefix;
+  return node()->dimension() == MassDimension && node()->representative() == KilogramRepresentative && *(node()->prefix()) == KiloPrefix;
 }
 
 bool Unit::IsISSpeed(Expression & e) {