Add test/data/artificial to seed_corpora.txt
diff --git a/fuzz/c/std/seed_corpora.txt b/fuzz/c/std/seed_corpora.txt
index 809e9fd..b295144 100644
--- a/fuzz/c/std/seed_corpora.txt
+++ b/fuzz/c/std/seed_corpora.txt
@@ -11,6 +11,6 @@
# This file is not used by Wuffs per se, but it is used by the "projects/wuffs"
# directory in the https://github.com/google/oss-fuzz repository.
-gif: test/data/*.gif
-gzip: test/data/*.gz
+gif: test/data/*.gif test/data/artificial/*.gif
+gzip: test/data/*.gz test/data/artificial/*.gz
zlib: test/data/*.zlib
