diff --git a/test/T310-emacs.sh b/test/T310-emacs.sh
index ac966e52..c3024021 100755
--- a/test/T310-emacs.sh
+++ b/test/T310-emacs.sh
@@ -483,7 +483,7 @@ test_expect_equal_file OUTPUT EXPECTED
 test_begin_subtest "Reply within emacs to an html-only message"
 add_message '[content-type]="text/html"' \
 	    '[body]="Hi,<br />This is an <b>HTML</b> test message.<br /><br />OK?"'
-test_emacs "(let ((message-hidden-headers '()) (mm-text-html-renderer 'html2text))
+test_emacs "(let ((message-hidden-headers '()))
 	    (notmuch-show \"id:${gen_msg_id}\")
 	    (notmuch-show-reply)
 	    (test-output))"
diff --git a/test/test-lib.el b/test/test-lib.el
index 36afe630..bbc03cba 100644
--- a/test/test-lib.el
+++ b/test/test-lib.el
@@ -181,3 +181,8 @@ nothing."
 ;; suite
 (setq notmuch-tag-deleted-formats
       '((".*" nil)))
+
+;; force a common html renderer, to avoid test variations between
+;; environments
+
+(setq mm-text-html-renderer 'html2text)