diff --git a/unix/console.c b/unix/console.c
index 75e51a7f..286ecf29 100644
--- a/unix/console.c
+++ b/unix/console.c
@@ -109,7 +109,7 @@ SeatPromptResult console_confirm_ssh_host_key(
 {
     char line[32];
     struct termios cf;
-    const char *prompt;
+    const char *prompt = NULL;
 
     stdio_sink errsink[1];
     stdio_sink_init(errsink, stderr);
@@ -146,6 +146,7 @@ SeatPromptResult console_confirm_ssh_host_key(
             break;
         }
     }
+    assert(prompt); /* something in the SeatDialogText should have set this */
 
     while (true) {
         fprintf(stderr,