diff --git a/src/cosmopower.cpp b/src/cosmopower.cpp
index 8544c25..8e6b940 100644
--- a/src/cosmopower.cpp
+++ b/src/cosmopower.cpp
@@ -172,9 +172,10 @@ double CosmoPower::powerHuWiggles(double k)
   double beta_c = ehu.beta_c;
   double alpha_b = ehu.alpha_b;
   double beta_b = ehu.beta_b;
-  double s_tilde = s * pow(1 + pow(ehu.beta_node / (k * s), 3), -1./3);
-  
   double xx = k * s;  
+
+  double s_tilde = s * pow(1 + pow(ehu.beta_node / (xx), 3), -1./3);
+  
   double f = 1 / (1 + pow(xx / 5.4, 4));
   double q = k / (13.41 * k_eq);
   double T_c = f * T_tilde_0(q, 1, beta_c) + (1 - f) * T_tilde_0(q, alpha_c, beta_c);