diff --git a/test/T670-duplicate-mid.sh b/test/T670-duplicate-mid.sh
index c198c506..bf8cc3a8 100755
--- a/test/T670-duplicate-mid.sh
+++ b/test/T670-duplicate-mid.sh
@@ -47,6 +47,16 @@ EOF
 notmuch search --output=files subject:'"message 2"' | notmuch_dir_sanitize > OUTPUT
 test_expect_equal_file EXPECTED OUTPUT
 
+test_begin_subtest 'Regexp search for second subject'
+test_subtest_known_broken
+cat <<EOF >EXPECTED
+MAIL_DIR/copy0
+MAIL_DIR/copy1
+MAIL_DIR/copy2
+EOF
+notmuch search --output=files 'subject:"/message 2/"' | notmuch_dir_sanitize > OUTPUT
+test_expect_equal_file EXPECTED OUTPUT
+
 add_message '[id]="duplicate"' '[body]="sekrit" [filename]=copy3'
 test_begin_subtest 'search for body in duplicate file'
 cat <<EOF >EXPECTED