diff --git a/test/doctest-auto b/test/doctest-auto
index 9b736591c..e860adeda 100755
--- a/test/doctest-auto
+++ b/test/doctest-auto
@@ -4,6 +4,9 @@
 
 set -e -o pipefail
 
+# Ensure reproducible output (#1849)
+export LC_ALL=C
+
 cat <<EOF
 # AUTOGENERATED -- DO NOT EDIT