diff --git a/libraries/Fraction/fraction.cpp b/libraries/Fraction/fraction.cpp
index f1326f87..40a662ae 100644
--- a/libraries/Fraction/fraction.cpp
+++ b/libraries/Fraction/fraction.cpp
@@ -227,14 +227,14 @@ double Fraction::toAngle()
 
 // the mediant is a fraction that is always between 2 fractions
 // at least if within precission.
-Fraction Fraction::mediant(Fraction a, Fraction b)
+Fraction Fraction::mediant(const Fraction &a, const Fraction &b)
 {
     return Fraction(a.n + b.n, a.d + b.d);
 }
 
 // approximate a fraction with defined denominator
 // sort of setDenominator(uint16_t den);
-Fraction Fraction::setDenominator(Fraction a, uint16_t b)
+Fraction Fraction::setDenominator(const Fraction &a, uint16_t b)
 {
     int32_t n = round((a.n * b * 1.0) / a.d);
     int32_t d = b;
@@ -245,7 +245,7 @@ Fraction Fraction::setDenominator(Fraction a, uint16_t b)
 ////////////////////////////////////////////////////////////////
 // PRIVATE
 // http://en.wikipedia.org/wiki/Binary_GCD_algorithm
-int32_t Fraction::gcd(int32_t a , int32_t b)
+int32_t& Fraction::gcd(int32_t &a , int32_t &b)
 {
     long c;
     while ( a != 0 )
diff --git a/libraries/Fraction/fraction.h b/libraries/Fraction/fraction.h
index fd08d5c4..b5e707ff 100644
--- a/libraries/Fraction/fraction.h
+++ b/libraries/Fraction/fraction.h
@@ -56,15 +56,15 @@ public:
     bool isProper();    // abs(f) < 1
     double toAngle();
 
-    static Fraction mediant(Fraction, Fraction);
+    static Fraction mediant(const Fraction&, const Fraction&);
     // approximate a fraction with defined denominator
-    static Fraction setDenominator(Fraction, uint16_t);
+    static Fraction setDenominator(const Fraction&, uint16_t);
 
 
-private:
+protected:
     void simplify();
     double fractionize(double);
-    int32_t gcd(int32_t, int32_t);
+    int32_t& gcd(int32_t&, int32_t&);
 
     int32_t n;
     int32_t d;