--- old/src/hotspot/share/classfile/systemDictionary.cpp	2018-04-10 16:58:49.768142000 +0200
+++ new/src/hotspot/share/classfile/systemDictionary.cpp	2018-04-10 16:58:49.321073000 +0200
@@ -2170,7 +2170,6 @@
       if ((defining == true) || (k != check)) {
         linkage_error1 = "loader ";
         linkage_error2 = " attempted duplicate class definition for ";
-        guarantee(check->class_loader() == class_loader(), "Per construction. Else report the other loader.");
       } else {
         return;
       }
@@ -3107,18 +3106,10 @@
   NOT_PRODUCT(SystemDictionary::verify());
 }
 
-// Return string to give helpful intformation about a classloader.
 // Caller needs ResourceMark.
 const char* SystemDictionary::loader_name(const oop loader) {
-#if INCLUDE_CDS
-  if (DumpSharedSpaces) {
-    // Describe_external() calls assert(is_instance...) in various places,
-    // which may fail with DumpSharedSpaces.
-    if ((loader) == NULL) return "<bootloader>";
-    return InstanceKlass::cast((loader)->klass())->name()->as_C_string();
-  }
-#endif
-  return java_lang_ClassLoader::describe_external(loader);
+  return ((loader) == NULL ? "<bootloader>" :
+          InstanceKlass::cast((loader)->klass())->name()->as_C_string());
 }
 
 // caller needs ResourceMark