diff --git a/psychopy/app/builder/builder.py b/psychopy/app/builder/builder.py
index 74d34b8b21..8bdc31f217 100644
--- a/psychopy/app/builder/builder.py
+++ b/psychopy/app/builder/builder.py
@@ -124,7 +124,9 @@ def doCheck(self):
             # then check if the process ended
             # self.exit
         for line in self.proc.stderr.readlines():
-            sys.stdout.write(line)
+            self.queue.put(line)
+            if not line:
+                break
         return True
 
     def getBuffer(self):