diff -r 608e332e33e8 -r bdf8f77aad3a src/hotspot/share/prims/jvm.cpp
--- a/src/hotspot/share/prims/jvm.cpp	Thu Mar 01 15:47:48 2018 +0100
+++ b/src/hotspot/share/prims/jvm.cpp	Thu Mar 01 17:00:23 2018 +0100
@@ -2279,7 +2279,7 @@
     ConstantPool* cp = InstanceKlass::cast(k)->constants();
     for (int index = cp->length() - 1; index >= 0; index--) {
       constantTag tag = cp->tag_at(index);
-      types[index] = (tag.is_unresolved_klass()) ? JVM_CONSTANT_Class : tag.value();
+      types[index] = (tag.is_unresolved_klass()) ? (unsigned char) JVM_CONSTANT_Class : tag.value();
     }
   }
 JVM_END