diff --git a/include/hpp/statistics/bin.hh b/include/hpp/statistics/bin.hh
index 72158635dc7d88f228f7840e15098fa6c7525cd7..ac6421f2ce4d4a15068b1bcf0f6f08768f682fdd 100644
--- a/include/hpp/statistics/bin.hh
+++ b/include/hpp/statistics/bin.hh
@@ -36,21 +36,21 @@ namespace hpp {
     {
       public:
         /// Return the number of element in the bin.
-        size_t freq () const
+        const std::size_t& freq () const
         {
           return freq_;
         }
 
         /// Add an occurence
         /// \return The frequency after increment;
-        size_t operator ++()
+        std::size_t operator ++()
         {
           return ++freq_;
         }
 
         /// Add an occurence
         /// \return The frequency before increment;
-        size_t operator ++(int)
+        std::size_t operator ++(int)
         {
           return freq_++;
         }
@@ -70,7 +70,7 @@ namespace hpp {
 
       private:
         /// The number of occurence.
-        size_t freq_;
+        std::size_t freq_;
     };
 
     inline std::ostream& operator<< (std::ostream& os, const hpp::statistics::Bin& b)
@@ -93,7 +93,7 @@ namespace hpp {
         /// \param bin a Bin for which only the value is useful.
         /// \note  It searches for the equivalent Bin is the set and
         ///        returns the frequency of the result.
-        virtual size_t freq (const T& bin) const;
+        virtual std::size_t freq (const T& bin) const;
 
         /// Return the relative frequency of a Bin.
         /// \param bin a Bin for which only the value is useful.
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 6852c3581868f8875ae9978e27d042e4c830fe00..f7b0f8f3a651da5f47e171d9691d384cee1040c9 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -20,7 +20,6 @@
 SET(LIBRARY_NAME ${PROJECT_NAME})
 
 ADD_LIBRARY(${LIBRARY_NAME} SHARED
-  bin.cc
   success-bin.cc
 )