diff --git a/src/tools/rustdoc-gui/tester.js b/src/tools/rustdoc-gui/tester.js
index 3f83aa425dff..f0e5aef0ec15 100644
--- a/src/tools/rustdoc-gui/tester.js
+++ b/src/tools/rustdoc-gui/tester.js
@@ -75,7 +75,7 @@ function print_test_successful() {
 }
 
 function print_test_erroneous() {
-    process.stdout.write("F");
+    process.stderr.write("F");
 }
 
 async function main(argv) {