diff --git a/src/smt/smt_context.h b/src/smt/smt_context.h
index 63df29d29..0e4cdde44 100644
--- a/src/smt/smt_context.h
+++ b/src/smt/smt_context.h
@@ -137,7 +137,7 @@ namespace smt {
         scoped_ptr<base_dependent_expr_state> m_fmls;
 
         svector<double> m_lit_scores[2];
-        vector<expr_ref_vector> m_recorded_cubes;
+        vector<expr_ref_vector>* m_recorded_cubes = nullptr;
 
 
         // -----------------------------------
diff --git a/src/smt/smt_internalizer.cpp b/src/smt/smt_internalizer.cpp
index 45c174f65..e1eda24f9 100644
--- a/src/smt/smt_internalizer.cpp
+++ b/src/smt/smt_internalizer.cpp
@@ -967,6 +967,8 @@ namespace smt {
 
     // following the pattern of solver::persist_clause in src/sat/smt/user_solver.cpp
     void context::record_cube(unsigned num_lits, literal const *lits) {
+        if (!m_recorded_cubes)
+            return;
         expr_ref_vector cube(m);
         for (unsigned i = 0; i < num_lits; ++i) {
             literal lit = lits[i];
@@ -976,7 +978,7 @@ namespace smt {
                 e = m.mk_not(e);  // only negate positive literal
             cube.push_back(e);
         }
-        m_recorded_cubes.push_back(cube);
+        m_recorded_cubes->push_back(cube);
     }
 
     void context::add_scores(unsigned n, literal const *lits) {
diff --git a/src/smt/smt_parallel.cpp b/src/smt/smt_parallel.cpp
index c0c1f067f..faf45af79 100644
--- a/src/smt/smt_parallel.cpp
+++ b/src/smt/smt_parallel.cpp
@@ -67,6 +67,8 @@ namespace smt {
     lbool parallel::param_generator::run_prefix_step() {
         IF_VERBOSE(1, verbose_stream() << " Param generator running prefix step\n");
         ctx->get_fparams().m_max_conflicts = m_max_prefix_conflicts;
+        m_recorded_cubes.reset();
+        ctx->m_recorded_cubes = &m_recorded_cubes;
         lbool r = l_undef;
         try {
             r = ctx->check();
@@ -110,7 +112,7 @@ namespace smt {
             double score = 0.0;
 
             // replay the cube (negation of the clause)
-            for (expr_ref_vector const& cube : probe_ctx->m_recorded_cubes) {
+            for (expr_ref_vector const& cube : m_recorded_cubes) {
                 lbool r = probe_ctx->check(cube.size(), cube.data());               
                 unsigned conflicts = probe_ctx->m_stats.m_num_conflicts;                
                 unsigned decisions = probe_ctx->m_stats.m_num_decisions;
diff --git a/src/smt/smt_parallel.h b/src/smt/smt_parallel.h
index e0ecb874a..27111c0bd 100644
--- a/src/smt/smt_parallel.h
+++ b/src/smt/smt_parallel.h
@@ -128,6 +128,7 @@ namespace smt {
             unsigned m_max_prefix_conflicts = 1000;
 
             scoped_ptr<context> m_prefix_solver;
+            vector<expr_ref_vector> m_recorded_cubes;
             params_ref m_p;
             param_values m_param_state;