--- a/langtools/src/share/classes/com/sun/tools/javac/comp/MemberEnter.java	Fri Jan 14 09:45:52 2011 +0000
+++ b/langtools/src/share/classes/com/sun/tools/javac/comp/MemberEnter.java	Fri Jan 14 09:46:44 2011 +0000
@@ -781,8 +781,8 @@
                     types.isSameType(c.type, syms.polymorphicSignatureType)) {
                 if (!target.hasMethodHandles()) {
                     // Somebody is compiling JDK7 source code to a JDK6 target.
-                    // Make it a strict warning, since it is unlikely but important.
-                    log.strictWarning(env.tree.pos(),
+                    // Make it an error, since it is unlikely but important.
+                    log.error(env.tree.pos(),
                             "wrong.target.for.polymorphic.signature.definition",
                             target.name);
                 }