diff --git a/unix/uxpgnt.c b/unix/uxpgnt.c
index 14f1366c..b8738fac 100644
--- a/unix/uxpgnt.c
+++ b/unix/uxpgnt.c
@@ -136,6 +136,7 @@ static void usage(void)
     printf("  -D           delete all keys from the agent\n");
     printf("Other options:\n");
     printf("  -v           verbose mode (in agent mode)\n");
+    printf("  -s -c        force POSIX or C shell syntax (in agent mode)\n");
     exit(1);
 }