diff --git a/src/sat/sat_solver/inc_sat_solver.cpp b/src/sat/sat_solver/inc_sat_solver.cpp
index 097d3f0fa..5de64b496 100644
--- a/src/sat/sat_solver/inc_sat_solver.cpp
+++ b/src/sat/sat_solver/inc_sat_solver.cpp
@@ -311,7 +311,10 @@ public:
     expr_ref_vector cube(expr_ref_vector& vs, unsigned backtrack_level) override {
         if (!is_internalized()) {
             lbool r = internalize_formulas();
-            if (r != l_true) return expr_ref_vector(m);
+            if (r != l_true) {
+                IF_VERBOSE(0, verbose_stream() << "internalize produced " << r << "\n");
+                return expr_ref_vector(m);
+            }
         }
         convert_internalized();
         obj_hashtable<expr> _vs;
@@ -329,6 +332,7 @@ public:
             return result;
         }
         if (result == l_true) {
+            IF_VERBOSE(1, verbose_stream() << "formulas are SAT\n");
             return expr_ref_vector(m);
         }        
         expr_ref_vector fmls(m);
@@ -345,6 +349,7 @@ public:
                 vs.push_back(x);
             }
         }
+        if (fmls.empty()) { IF_VERBOSE(0, verbose_stream() << "no literals were produced in cube\n"); }
         return fmls;
     }