diff --git a/APPL/Shared/Shared.inc b/APPL/Shared/Shared.inc
index 347e269ad4..315c557f82 100644
--- a/APPL/Shared/Shared.inc
+++ b/APPL/Shared/Shared.inc
@@ -1238,6 +1238,10 @@ var cache = {
 // Datum functies
 Date.prototype.toSQL = function toSQL(withTime)
 {
+    var year = this.getFullYear();
+    if (year < 1000 || year > 9999)
+        shared.internal_error("Invalid year " + this.toLocaleString()); // Net iets minder erg dan ORA-01830
+
     var str = padout(this.getDate()) + "-" + padout(this.getMonth() + 1) + "-" + padout(this.getFullYear())
     if (withTime)
     {