diff --git a/src/opt/maxlex.cpp b/src/opt/maxlex.cpp
index 1ee9db090..b2799f1c8 100644
--- a/src/opt/maxlex.cpp
+++ b/src/opt/maxlex.cpp
@@ -127,7 +127,7 @@ namespace opt {
             }
             model_ref mdl;
             s().get_model(mdl);
-            update_assignment(mdl);           
+            if (mdl) update_assignment(mdl);           
         }
 
         lbool maxlex1() {