diff --git a/Packages/Core/include/CORE/BigRat.h b/Packages/Core/include/CORE/BigRat.h
index 44d2812fcb4..7a75438b72d 100644
--- a/Packages/Core/include/CORE/BigRat.h
+++ b/Packages/Core/include/CORE/BigRat.h
@@ -308,9 +308,13 @@ public:
     return mpq_set_str(get_mp(), s, base);
   }
   /// convert to <tt>std::string</tt>
-  std::string get_str(int base = 10) const {
-    _alloc_cstr t(mpq_get_str(0, base, get_mp()));
-    return std::string(t.str);
+  std::string get_str(int base Bi= 10) const {
+    int n = mpz_sizeinbase(mpq_numref(get_mp()), base) + mpz_sizeinbase(mpq_denref(get_mp()), base)+ 3;
+    char *buffer = new char[n];
+    mpq_get_str(buffer, base, get_mp());
+    std::string result(buffer);
+    delete [] buffer;
+    return result;
   }
   //@}