diff --git a/eo/src/ga/make_ga.h b/eo/src/ga/make_ga.h
index ce594903f..206094881 100644
--- a/eo/src/ga/make_ga.h
+++ b/eo/src/ga/make_ga.h
@@ -57,8 +57,8 @@
  */
 
 // the genotypes
-eoInit<eoBit<double> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<double> _eo);
-  eoInit<eoBit<eoMinimizingFitness> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<eoMinimizingFitness> _eo);
+eoInit<eoBit<double> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<double> _eo, float _bias=0.5);
+  eoInit<eoBit<eoMinimizingFitness> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<eoMinimizingFitness> _eo, float _bias=0.5);
 
 // the operators
 eoGenOp<eoBit<double> >&  make_op(eoParser& _parser, eoState& _state, eoInit<eoBit<double> >& _init);
diff --git a/eo/src/ga/make_genotype_ga.cpp b/eo/src/ga/make_genotype_ga.cpp
index 4f9e69ef1..3344a8d87 100644
--- a/eo/src/ga/make_genotype_ga.cpp
+++ b/eo/src/ga/make_genotype_ga.cpp
@@ -45,11 +45,11 @@
 
 /// The following function merely call the templatized do_* functions above
 
-eoInit<eoBit<double> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<double> _eo)
+eoInit<eoBit<double> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<double> _eo, float _bias)
 {
-  return do_make_genotype(_parser, _state, _eo);
+    return do_make_genotype(_parser, _state, _eo, _bias);
 }
-eoInit<eoBit<eoMinimizingFitness> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<eoMinimizingFitness> _eo)
+eoInit<eoBit<eoMinimizingFitness> > & make_genotype(eoParser& _parser, eoState& _state, eoBit<eoMinimizingFitness> _eo, float _bias)
 {
-  return do_make_genotype(_parser, _state, _eo);
+    return do_make_genotype(_parser, _state, _eo, _bias);
 }
diff --git a/eo/src/ga/make_genotype_ga.h b/eo/src/ga/make_genotype_ga.h
index ea1b20054..fad4f7563 100644
--- a/eo/src/ga/make_genotype_ga.h
+++ b/eo/src/ga/make_genotype_ga.h
@@ -60,7 +60,7 @@
  * @ingroup Builders
 */
 template <class EOT>
-eoInit<EOT> & do_make_genotype(eoParser& _parser, eoState& _state, EOT)
+eoInit<EOT> & do_make_genotype(eoParser& _parser, eoState& _state, EOT, float _bias=0.5)
 {
   // for bitstring, only thing needed is the size
   // but it might have been already read in the definition fo the performance
@@ -68,7 +68,7 @@ eoInit<EOT> & do_make_genotype(eoParser& _parser, eoState& _state, EOT)
 
   // Then we can built a bitstring random initializer
   // based on boolean_generator class (see utils/rnd_generator.h)
-  eoBooleanGenerator * gen = new eoBooleanGenerator;
+  eoBooleanGenerator * gen = new eoBooleanGenerator(_bias);
   _state.storeFunctor(gen);
   eoInitFixedLength<EOT>* init = new eoInitFixedLength<EOT>(theSize, *gen);
   // store in state