diff --git a/src/nlsat/nlsat_explain.cpp b/src/nlsat/nlsat_explain.cpp
index d30eb5106..e6bbdad6e 100644
--- a/src/nlsat/nlsat_explain.cpp
+++ b/src/nlsat/nlsat_explain.cpp
@@ -48,6 +48,7 @@ namespace nlsat {
         bool                    m_minimize_cores;
         bool                    m_factor;
         bool                    m_add_all_coeffs;
+        bool                    m_add_zero_disc;
         bool                    m_signed_project;
         bool                    m_cell_sample;
 
@@ -159,6 +160,7 @@ namespace nlsat {
             m_full_dimensional = false;
             m_minimize_cores   = false;
             m_add_all_coeffs   = true;
+            m_add_zero_disc = true;
             m_signed_project   = false;
         }
 
@@ -456,6 +458,7 @@ namespace nlsat {
                 TRACE(nlsat_explain, tout << "lc: " << lc << " reduct: " << reduct << "\n";);
                 insert_fresh_factors_in_todo(lc);
                 if (!is_zero(lc) && sign(lc)) {
+                    insert_fresh_factors_in_todo(lc);
                     TRACE(nlsat_explain, tout << "lc does no vaninsh\n";);
                     return;
                 }
@@ -830,6 +833,9 @@ namespace nlsat {
                     TRACE(nlsat_explain, tout << "done, psc is a constant\n";);
                     return;
                 }
+                if (m_add_zero_disc && !sign(s)) {                    
+                    add_zero_assumption(s);
+                }
                 TRACE(nlsat_explain, 
                       tout << "adding v-psc of\n";
                       display(tout, p);
@@ -1897,6 +1903,10 @@ namespace nlsat {
         m_imp->m_add_all_coeffs = f;
     }
 
+    void explain::set_add_zero_disc(bool f) {
+        m_imp->m_add_zero_disc = f;
+    }
+
     void explain::set_signed_project(bool f) {
         m_imp->m_signed_project = f;
     }
diff --git a/src/nlsat/nlsat_explain.h b/src/nlsat/nlsat_explain.h
index 2c3adfcb2..e28e0f8a3 100644
--- a/src/nlsat/nlsat_explain.h
+++ b/src/nlsat/nlsat_explain.h
@@ -45,6 +45,7 @@ namespace nlsat {
         void set_minimize_cores(bool f);
         void set_factor(bool f);
         void set_add_all_coeffs(bool f);
+        void set_add_zero_disc(bool f);
         void set_signed_project(bool f);
 
         /**
diff --git a/src/nlsat/nlsat_params.pyg b/src/nlsat/nlsat_params.pyg
index 6478ba531..a5f91d2df 100644
--- a/src/nlsat/nlsat_params.pyg
+++ b/src/nlsat/nlsat_params.pyg
@@ -21,5 +21,7 @@ def_module_params('nlsat',
                           ('seed', UINT, 0, "random seed."),
                           ('factor', BOOL, True, "factor polynomials produced during conflict resolution."),
                           ('add_all_coeffs', BOOL, False, "add all polynomial coefficients during projection."),
+                          ('zero_disc', BOOL, True, "add_zero_assumption to the vanishing discriminant."),
                           ('known_sat_assignment_file_name', STRING, "", "the file name of a known solution: used for debugging only")
+                          
                           ))         
diff --git a/src/nlsat/nlsat_solver.cpp b/src/nlsat/nlsat_solver.cpp
index e4e29c4ea..0f374bfd1 100644
--- a/src/nlsat/nlsat_solver.cpp
+++ b/src/nlsat/nlsat_solver.cpp
@@ -311,6 +311,7 @@ namespace nlsat {
             m_explain.set_minimize_cores(min_cores);
             m_explain.set_factor(p.factor());
             m_explain.set_add_all_coeffs(p.add_all_coeffs());
+            m_explain.set_add_zero_disc(p.zero_disc());            
             m_am.updt_params(p.p);
         }