diff --git a/src/vim9compile.c b/src/vim9compile.c
index 77945fb..c89c37a 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2178,7 +2178,22 @@
 
 		if (isn == NULL)
 		    return FAIL;
-		isn->isn_arg.vartype = dest_type;
+		isn->isn_arg.storeindex.si_vartype = dest_type;
+		isn->isn_arg.storeindex.si_class = NULL;
+
+		if (dest_type == VAR_OBJECT)
+		{
+		    class_T *cl = (class_T *)lhs->lhs_type->tt_member;
+
+		    if (cl->class_flags & CLASS_INTERFACE)
+		    {
+			// "this.value": load "this" object and get the value
+			// at index for an object or class member get the type
+			// of the member
+			isn->isn_arg.storeindex.si_class = cl;
+			++cl->class_refcount;
+		    }
+		}
 	    }
 	}
 	else if (range)