diff --git a/src/solver.cpp b/src/solver.cpp
index 6d8cc61a..e917b3c8 100644
--- a/src/solver.cpp
+++ b/src/solver.cpp
@@ -701,6 +701,7 @@ int Solver::call_external_solve_and_check_results (bool preprocess_only) {
   if (!res) {
     external->reset_assumptions ();
     external->reset_constraint ();
+    external->reset_concluded ();
   }
   return res;
 }