diff --git a/src/solver/check_sat_result.cpp b/src/solver/check_sat_result.cpp
index 71bd24747..d29e0f2bd 100644
--- a/src/solver/check_sat_result.cpp
+++ b/src/solver/check_sat_result.cpp
@@ -21,7 +21,8 @@ Notes:
 void check_sat_result::set_reason_unknown(event_handler& eh) {
     switch (eh.caller_id()) {
     case UNSET_EH_CALLER: 
-        set_reason_unknown("unclassifed exception");
+        if (reason_unknown() == "")
+            set_reason_unknown("unclassifed exception");
         break;
     case CTRL_C_EH_CALLER:
         set_reason_unknown("interrupted from keyboard");