diff --git a/zebra-network/proptest-regressions/protocol/external/types.txt b/zebra-network/proptest-regressions/protocol/external/types.txt
new file mode 100644
index 00000000..dad59b4a
--- /dev/null
+++ b/zebra-network/proptest-regressions/protocol/external/types.txt
@@ -0,0 +1,7 @@
+# Seeds for failure cases proptest has generated in the past. It is
+# automatically read and these particular cases re-run before any
+# novel cases are generated.
+#
+# It is recommended to check this file in to source control so that
+# everyone who runs the test benefits from these saved cases.
+cc 1c86ac8e13c37c728a712e43a95610c77b1d51118eaac496f9a53862c0ed4ded # shrinks to data = [0, 0, 0, 0]