--- old/src/hotspot/share/classfile/moduleEntry.cpp	2020-08-31 08:10:34.454444922 -0700
+++ new/src/hotspot/share/classfile/moduleEntry.cpp	2020-08-31 08:10:34.234436640 -0700
@@ -487,6 +487,7 @@
 }
 
 static int compare_module_by_name(ModuleEntry* a, ModuleEntry* b) {
+  assert(a == b || a->name() != b->name(), "no duplicated names");
   return a->name()->fast_compare(b->name());
 }