--- a/src/hotspot/share/classfile/verifier.cpp	Thu Jul 12 16:30:47 2018 +0200
+++ b/src/hotspot/share/classfile/verifier.cpp	Wed Jul 11 16:11:10 2018 +0200
@@ -719,7 +719,8 @@
         ResourceMark rm(THREAD);
         LogStream ls(lt);
         current_frame.print_on(&ls);
-        lt.print("offset = %d,  opcode = %s", bci, Bytecodes::name(opcode));
+        lt.print("offset = %d,  opcode = %s", bci,
+                 opcode == Bytecodes::_illegal ? "illegal" : Bytecodes::name(opcode));
       }
 
       // Make sure wide instruction is in correct format