diff --git a/src/model/ChamberSphere.cpp b/src/model/ChamberSphere.cpp
index 6971e7713..b3a086c72 100644
--- a/src/model/ChamberSphere.cpp
+++ b/src/model/ChamberSphere.cpp
@@ -119,8 +119,16 @@ void ChamberSphere::get_elastance_values(std::vector<double>& parameters) {
   const auto T_cardiac = model->cardiac_cycle_period;
   const auto t_in_cycle = fmod(model->time, T_cardiac);
 
-  const double S_plus = 0.5 * (1.0 + tanh((t_in_cycle - tsys) / steepness));
-  const double S_minus = 0.5 * (1.0 - tanh((t_in_cycle - tdias) / steepness));
+  
+  auto warp_signed = [T_cardiac](double dt){
+    return fmod(dt + 1.5 * T_cardiac, T_cardiac) - 0.5 * T_cardiac;
+  };
+
+  const double phase_tsys = warp_signed(t_in_cycle - tsys);
+  const double phase_tdias = warp_signed(t_in_cycle - tdias);
+
+  const double S_plus = 0.5 * (1.0 + tanh((phase_tsys) / steepness));
+  const double S_minus = 0.5 * (1.0 - tanh((phase_tdias - tdias) / steepness));
 
   // indicator function
   const double f = S_plus * S_minus;