diff --git a/src/sat/smt/polysat/viable.cpp b/src/sat/smt/polysat/viable.cpp
index 7a7deb573..dedaa53be 100644
--- a/src/sat/smt/polysat/viable.cpp
+++ b/src/sat/smt/polysat/viable.cpp
@@ -665,10 +665,12 @@ namespace polysat {
             switch (m_projection()) {
             case l_true:
                 // propagated interval onto subslice
+                result.reset();
                 m_projection.explain(result);
                 break;
             case l_false:
                 // conflict (projected interval is full)
+                result.reset();
                 m_projection.explain(result);
                 break;
             case l_undef: