diff --git a/ogs5py/ogs.py b/ogs5py/ogs.py
index 081718e..eece481 100644
--- a/ogs5py/ogs.py
+++ b/ogs5py/ogs.py
@@ -1144,15 +1144,16 @@ def run_model(
             " ".join(args),
             timeout=timeout,
             logfile=out,
+            encoding=out.encoding,
             cwd=os.path.abspath(self.task_root),
         )
         # wait for ogs to finish
         child.expect(pexpect.EOF)
+        child.close()
+        success = child.exitstatus == 0
         # close the output stream
         out.close()
 
-        success = "Simulation time" in out.last_line
-
         if not save_log:
             os.remove(log)