diff --git a/Tools/autotest/pysim/util.py b/Tools/autotest/pysim/util.py
index bab8f3dc9d..fdbddd78a4 100644
--- a/Tools/autotest/pysim/util.py
+++ b/Tools/autotest/pysim/util.py
@@ -415,7 +415,10 @@ class PSpawnStdPrettyPrinter(object):
 
     def write(self, data):
         self.buffer += data
-        for line in self.buffer.split("\n"):
+        lines = self.buffer.split("\n")
+        self.buffer = lines[-1]
+        lines.pop()
+        for line in lines:
             self.print_prefixed_line(line)
 
     def print_prefixed_line(self, line):