diff --git a/mozilla/js/src/xpconnect/shell/xpcshell.cpp b/mozilla/js/src/xpconnect/shell/xpcshell.cpp
index 7b5b471af12..d86ae37796f 100644
--- a/mozilla/js/src/xpconnect/shell/xpcshell.cpp
+++ b/mozilla/js/src/xpconnect/shell/xpcshell.cpp
@@ -964,6 +964,10 @@ main(int argc, char **argv, char **envp)
     int result;
     nsresult rv;
 
+    // unbuffer stdout so that output is in the correct order; note that stderr
+    // is unbuffered by default
+    setbuf(stdout, 0);
+
     gErrFile = stderr;
     gOutFile = stdout;
     {