diff --git a/src/vim9.h b/src/vim9.h
index 0f1a9ab..49103ba 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -60,6 +60,7 @@
 
     ISN_UNLET,		// unlet variable isn_arg.unlet.ul_name
     ISN_UNLETENV,	// unlet environment variable isn_arg.unlet.ul_name
+    ISN_UNLETINDEX,	// unlet item of list or dict
 
     ISN_LOCKCONST,	// lock constant value