diff --git a/server-fn.c b/server-fn.c
index a025bf0a..fb40a624 100644
--- a/server-fn.c
+++ b/server-fn.c
@@ -214,7 +214,7 @@ server_unlock(const char *s)
 wrong:
 	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
 		c = ARRAY_ITEM(&clients, i);
-		if (c == NULL)
+                if (c == NULL || c->prompt_buffer == NULL)
 			continue;
 
 		*c->prompt_buffer = '\0';