diff --git a/Core/include/CORE/BigInt.h b/Core/include/CORE/BigInt.h
index fb1611c6896..268d92da402 100644
--- a/Core/include/CORE/BigInt.h
+++ b/Core/include/CORE/BigInt.h
@@ -46,7 +46,8 @@ public:
   BigIntRep() {
     mpz_init(mp);
   }
-  BigIntRep(const BigIntRep& z) {
+  // Note : should the copy-ctor be alloed at all ? [Sylvain Pion]
+  BigIntRep(const BigIntRep& z) : RCRepImpl<BigIntRep>() {
     mpz_init_set(mp, z.mp);
   }
   BigIntRep(signed char c) {
diff --git a/Core/include/CORE/BigRat.h b/Core/include/CORE/BigRat.h
index cbef059b057..4461825e108 100644
--- a/Core/include/CORE/BigRat.h
+++ b/Core/include/CORE/BigRat.h
@@ -43,7 +43,8 @@ public:
   BigRatRep() {
     mpq_init(mp);
   }
-  BigRatRep(const BigRatRep& z) {
+  // Note : should the copy-ctor be alloed at all ? [Sylvain Pion]
+  BigRatRep(const BigRatRep& z)  : RCRepImpl<BigRatRep>() {
     mpq_init(mp);
     mpq_set(mp, z.mp);
   }