diff --git a/include/BSMPT/minimum_tracer/minimum_tracer.h b/include/BSMPT/minimum_tracer/minimum_tracer.h
index eafb84ce..3da5a03e 100644
--- a/include/BSMPT/minimum_tracer/minimum_tracer.h
+++ b/include/BSMPT/minimum_tracer/minimum_tracer.h
@@ -18,6 +18,7 @@
 #include <BSMPT/utility/asciiplotter/asciiplotter.h>
 #include <BSMPT/utility/utility.h>
 #include <Eigen/Dense> // Eigenvalues matrix
+#include <algorithm>   // std::swap
 #include <chrono>
 #include <cmath>    // std::pow
 #include <memory>   // for shared_ptr
diff --git a/src/minimum_tracer/minimum_tracer.cpp b/src/minimum_tracer/minimum_tracer.cpp
index e806ad2f..155c3951 100644
--- a/src/minimum_tracer/minimum_tracer.cpp
+++ b/src/minimum_tracer/minimum_tracer.cpp
@@ -2401,6 +2401,12 @@ Vacuum::Vacuum(const double &T_lowIn,
       PhasesList[i].id = i;
     }
 
+    // impose that true vacuum at T = Tthigh has id = 0.
+    for (auto &phase : PhasesList)
+      if ((phase.T_high == T_high) and
+          (phase.Get(T_high).potential < PhasesList[0].Get(T_high).potential))
+        std::swap(PhasesList[0], phase);
+
     // identify coexisiting phase regions
     setCoexRegion(UseMultiStepPTMode); // can flip status_vacuum to error code