--- a/nashorn/src/jdk/nashorn/internal/codegen/CodeGenerator.java	Tue Jul 09 17:37:46 2013 +0530
+++ b/nashorn/src/jdk/nashorn/internal/codegen/CodeGenerator.java	Tue Jul 09 15:56:59 2013 +0200
@@ -1869,6 +1869,8 @@
                 method.store(tag);
                 method.conditionalJump(Condition.NE, true, defaultLabel);
             } else {
+                assert tag.getSymbolType().isObject();
+                method.convert(Type.OBJECT); //e.g. 1 literal pushed and tag is object
                 method.store(tag);
             }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nashorn/test/script/basic/JDK-8020124.js	Tue Jul 09 15:56:59 2013 +0200
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ * 
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ * 
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ * 
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ * 
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * JDK-8020124: explicit conversion needed for switch tag
+ *
+ * @test
+ * @run
+ */
+
+x = {};
+Function("switch((a? x = 1 : 3)) { default: return; }")