diff --git a/src/elasticity/materials/materials.hpp b/src/elasticity/materials/materials.hpp
index 741ece3852e08d28ef6b53d8cffa6e3b3432ecad..fa7f325d650164ee4566f38a27762dfd6864f556 100644
--- a/src/elasticity/materials/materials.hpp
+++ b/src/elasticity/materials/materials.hpp
@@ -127,9 +127,11 @@ namespace mat {
            + sqrt(gamma[0]) * (One - Product(Q[0], Q[0]));
       return AD;
     } else if (name == "Quarteroni2") {
-      AD = (1 / gamma[0]) * Product(Q[0], Q[0])
-           + scale_gamma * sqrt(gamma[0]) * Product(Q[1], Q[1])
-           + (sqrt(gamma[0]) / scale_gamma) * Product(Q[2], Q[2]);
+      if (1+gamma[0] < 0)
+	return One;
+      AD = (1 / (1+gamma[0])) * Product(Q[0], Q[0])
+           + scale_gamma * sqrt(1+gamma[0]) * Product(Q[1], Q[1])
+           + (sqrt(1+gamma[0]) / scale_gamma) * Product(Q[2], Q[2]);
       return AD;
     } else if (name == "") {
       AD = One - gamma[0] / (1 + gamma[0]) * Product(Q[0], Q[0])