diff --git a/gluon/dal.py b/gluon/dal.py
index 0dcd6fee..ecbe2bfe 100644
--- a/gluon/dal.py
+++ b/gluon/dal.py
@@ -7390,7 +7390,7 @@ def sqlhtml_validators(field):
         def repr_list(values, row=None): return', '.join(str(v) for v in (values or []))
         field.represent = field.represent or repr_list
     if field.unique:
-        requires.insert(0, validators.IS_NOT_IN_DB(db, field))
+        requires.append(validators.IS_NOT_IN_DB(db, field))
     sff = ['in', 'do', 'da', 'ti', 'de', 'bo']
     if field.notnull and not field_type[:2] in sff:
         requires.insert(0, validators.IS_NOT_EMPTY())
diff --git a/gluon/sqlhtml.py b/gluon/sqlhtml.py
index a1ba699f..9f106bde 100644
--- a/gluon/sqlhtml.py
+++ b/gluon/sqlhtml.py
@@ -94,8 +94,11 @@ def show_if(cond):
         return base, "[value!='%s']" % cond.second
     if cond.op.__name__ == 'CONTAINS':
         return base, "[value~='%s']" % cond.second
-    if cond.op.__name__ == 'BELONGS' and isinstance(cond.second, (list, tuple)):
-        return base, ','.join("[value='%s']" % (v) for v in cond.second)
+    if cond.op.__name__ == 'BELONGS':
+        if isinstance(cond.second, set):
+            cond.second = list(cond.second)
+        if isinstance(cond.second, (list, tuple)):
+            return base, ','.join("[value='%s']" % (v) for v in cond.second)
     raise RuntimeError("Not Implemented Error")