diff --git a/pytools/prefork.py b/pytools/prefork.py
index 49333371daf5120b371ffa4e422f9d2fe3f113d6..445ddf419f32caf534fa7c266530207318db03bd 100644
--- a/pytools/prefork.py
+++ b/pytools/prefork.py
@@ -76,7 +76,7 @@ def _recv_packet(sock, who="Process", partner="other end"):
 
     size, = unpack("I", size_bytes)
 
-    packet = ""
+    packet = b""
     while len(packet) < size:
         packet += sock.recv(size)