diff --git a/regress/misc/fuzz-harness/mux_fuzz_helper.c b/regress/misc/fuzz-harness/mux_fuzz_helper.c
index f81df7759..e80bc6dd7 100644
--- a/regress/misc/fuzz-harness/mux_fuzz_helper.c
+++ b/regress/misc/fuzz-harness/mux_fuzz_helper.c
@@ -44,6 +44,7 @@ volatile sig_atomic_t quit_pending = 0;
 
 /* Externs that sshconnect.c declares. */
 int hostkey_trusted = 0;
+int hostkey_untrusted = 0;
 
 /* Temporary: LSan off while upstream mux.c parse-chain leaks remain. */
 int