diff --git a/src/cmd_context/cmd_context.cpp b/src/cmd_context/cmd_context.cpp
index eafc771d0..e7a2f6795 100644
--- a/src/cmd_context/cmd_context.cpp
+++ b/src/cmd_context/cmd_context.cpp
@@ -553,7 +553,7 @@ void cmd_context::set_produce_models(bool f) {
 void cmd_context::set_produce_unsat_cores(bool f) {
     // can only be set before initialization
     SASSERT(!has_manager());
-    m_params.m_unsat_core = f;
+    m_params.m_unsat_core |= f;
 }
 
 void cmd_context::set_produce_proofs(bool f) {