diff --git a/spot/ltsmin/ltsmin.cc b/spot/ltsmin/ltsmin.cc
index 66919262d..894323873 100644
--- a/spot/ltsmin/ltsmin.cc
+++ b/spot/ltsmin/ltsmin.cc
@@ -45,6 +45,9 @@
 #include <spot/mc/ec.hh>
 #include <bricks/brick-hashset.h>
 #include <bricks/brick-hash.h>
+#include <spot/twaalgos/dot.hh>
+#include <spot/twa/twaproduct.hh>
+#include <spot/twaalgos/emptiness.hh>
 
 using namespace std::string_literals;
 
@@ -1706,13 +1709,13 @@ namespace spot
         relop oper;
 
 
-        // Now, left and (possibly) right are should refer atomic
+        // Now, left and (possibly) right may refer atomic
         // propositions or specific state inside of a process.
         // First check if it is a known atomic proposition
         it = std::find(k_aps.begin(), k_aps.end(), left);
         if (it != k_aps.end())
           {
-            // The aps is directly an AP of the system, we will just
+            // The ap is directly an AP of the system, we will just
             // have to detect if the variable is 0 or not.
             lval = std::distance(k_aps.begin(), it);
           }
@@ -1939,7 +1942,7 @@ namespace spot
   }
 
   ltsmin_kripkecube_ptr
-  ltsmin_model::kripkecube(const atomic_prop_set* to_observe,
+  ltsmin_model::kripkecube(std::vector<std::string> to_observe,
                            const formula dead, int compress) const
   {
     // Register the "dead" proposition.  There are three cases to
@@ -1958,26 +1961,19 @@ namespace spot
     else if (dead != spot::formula::tt())
       dead_ap = dead.ap_name();
 
-    // Build the set of observed propositons, i.e. those in the
-    // formula
-    std::vector<std::string> observed;
+    // Is dead proposition is already in to_observe?
     bool add_dead = true;
-    for (auto it: *to_observe)
-      {
-        observed.push_back(it.ap_name());
-
-        // Dead proposition is already in observed prop
-        if (it.ap_name().compare(dead_ap))
-          add_dead = false;
-      }
+    for (auto it: to_observe)
+      if (it.compare(dead_ap))
+        add_dead = false;
 
     if (dead_ap.compare("") != 0 && add_dead)
-      observed.push_back(dead_ap);
+      to_observe.push_back(dead_ap);
 
     // Finally build the system.
     return std::make_shared<spot::kripkecube<spot::cspins_state,
                                              spot::cspins_iterator>>
-      (iface, compress, observed, selfloopize, dead_ap);
+      (iface, compress, to_observe, selfloopize, dead_ap);
   }
 
   kripke_ptr
@@ -2016,6 +2012,12 @@ namespace spot
   ltsmin_model::modelcheck(ltsmin_kripkecube_ptr sys,
                            spot::twacube_ptr twa, bool compute_ctrx)
   {
+    // Must ensure that the two automata are working on the same
+    // set of atomic propositions.
+    assert(sys->get_ap().size() == twa->get_ap().size());
+    for (unsigned int i = 0; i < sys->get_ap().size(); ++i)
+      assert(sys->get_ap()[i].compare(twa->get_ap()[i]) == 0);
+
     ec_renault13lpar<cspins_state, cspins_iterator,
                      cspins_state_hash, cspins_state_equal> ec(*sys, twa);
     bool has_ctrx = ec.run();
diff --git a/spot/ltsmin/ltsmin.hh b/spot/ltsmin/ltsmin.hh
index bdbdf6375..38cb3a2d6 100644
--- a/spot/ltsmin/ltsmin.hh
+++ b/spot/ltsmin/ltsmin.hh
@@ -83,10 +83,9 @@ namespace spot
     // \brief The same as above but returns a kripkecube, i.e. a kripke
     // that can be use in parallel. Moreover, it support more ellaborated
     // atomic propositions such as "P.a == P.c"
-    ltsmin_kripkecube_ptr
-    kripkecube(const atomic_prop_set* to_observe,
-               formula dead = formula::tt(),
-               int compress = 0) const;
+    ltsmin_kripkecube_ptr kripkecube(std::vector<std::string> to_observe,
+                                     formula dead = formula::tt(),
+                                     int compress = 0) const;
 
     /// \brief Check for the emptiness between a system and a twa.
     /// Return a pair containing a boolean indicating wether a counterexample
diff --git a/tests/ltsmin/modelcheck.cc b/tests/ltsmin/modelcheck.cc
index 37ed85f3d..6d0a65e3a 100644
--- a/tests/ltsmin/modelcheck.cc
+++ b/tests/ltsmin/modelcheck.cc
@@ -29,6 +29,7 @@
 #include <spot/twaalgos/translate.hh>
 #include <spot/twaalgos/emptiness.hh>
 #include <spot/twaalgos/postproc.hh>
+#include <spot/twaalgos/are_isomorphic.hh>
 #include <spot/twa/twaproduct.hh>
 #include <spot/misc/timer.hh>
 #include <spot/misc/memusage.hh>
@@ -408,8 +409,8 @@ static int checked_main()
       spot::ltsmin_kripkecube_ptr modelcube = nullptr;
       try
         {
-          modelcube = spot::ltsmin_model::load(mc_options.model)
-            .kripkecube(&ap, deadf, mc_options.compress);
+           modelcube = spot::ltsmin_model::load(mc_options.model)
+            .kripkecube(propcube->get_ap(), deadf, mc_options.compress);
         }
       catch (std::runtime_error& e)
         {