diff --git a/benchexec/tools/hornix.py b/benchexec/tools/hornix.py
index 065b8cb8a..f3aba576c 100644
--- a/benchexec/tools/hornix.py
+++ b/benchexec/tools/hornix.py
@@ -38,7 +38,9 @@ def determine_result(self, run):
             return result.RESULT_TRUE_PROP
         elif "unsat" == line:
             return result.RESULT_FALSE_REACH
-        elif "unknown" == line:
+        elif "unknown" == line or line.startswith("UNKNOWN"):
             return result.RESULT_UNKNOWN
+        elif "timeout" == line:
+            return result.RESULT_TIMEOUT
         else:
             return result.RESULT_ERROR