diff --git a/adb/adb_auth_host.c b/adb/adb_auth_host.c
index a859199..1d48667 100644
--- a/adb/adb_auth_host.c
+++ b/adb/adb_auth_host.c
@@ -395,6 +395,11 @@
     unsigned int len;
     struct adb_private_key *key = node_to_item(node, struct adb_private_key, node);
 
+    if (token_size != TOKEN_SIZE) {
+        D("Unexpected token size %zd\n", token_size);
+        return 0;
+    }
+
     if (!RSA_sign(NID_sha1, token, token_size, sig, &len, key->rsa)) {
         return 0;
     }