diff --git a/src/option.c b/src/option.c
index 739b29a..de6e562 100644
--- a/src/option.c
+++ b/src/option.c
@@ -7199,6 +7199,9 @@
 	return OK;
     }
 
+    if (STRNCMP(optval, "s:", 2) == 0 && !SCRIPT_ID_VALID(current_sctx.sc_sid))
+	return FAIL;
+
     if (*optval == '{' || (in_vim9script() && *optval == '(')
 	    || (STRNCMP(optval, "function(", 9) == 0)
 	    || (STRNCMP(optval, "funcref(", 8) == 0))