diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 3dc0187..2beecba 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -632,6 +632,7 @@
                     pkg + ":", line, end="", file=sys.stderr, flush=True
                 )
             ),
+            _err_to_out=True,
         )