gistfile1.txt

diff --git a/src/core/interp.c b/src/core/interp.c
index a1bc5cf..a6216eb 100644
--- a/src/core/interp.c
+++ b/src/core/interp.c
@@ -50,6 +50,8 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
     /* The current call site we're constructing. */
     MVMCallsite *cur_callsite = NULL;
 
+    MVMuint16 op, last_op;
+    
     /* Stash addresses of current op, register base and SC deref base
      * in the TC; this will be used by anything that needs to switch
      * the current place we're interpreting. */
@@ -69,7 +71,7 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
 
     /* Enter runloop. */
     runloop: {
-        MVMuint16 op;
+        last_op = op;
 
 #if MVM_TRACING
         if (tracing_enabled) {
@@ -3962,7 +3964,7 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
                     goto NEXT;
                 }
 
-                MVM_panic(MVM_exitcode_invalidopcode, "Invalid opcode executed (corrupt bytecode stream?) opcode %u", op);
+                MVM_panic(MVM_exitcode_invalidopcode, "Invalid opcode executed (corrupt bytecode stream?) opcode %u, prev %u", op, last_op);
             }
 #endif
         }