diff --git a/src/vim9.h b/src/vim9.h
index 03f6dad..320e35b 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -499,12 +499,19 @@
     class_T	*cm_class;
     int		cm_idx;
 } classmember_T;
+
 // arguments to ISN_STOREINDEX
 typedef struct {
     vartype_T	si_vartype;
     class_T	*si_class;
 } storeindex_T;
 
+// arguments to ISN_LOCKUNLOCK
+typedef struct {
+    char_u	*string;	// for exec_command
+    int		is_arg;		// is lval_root a function arg
+} lockunlock_T;
+
 /*
  * Instruction
  */
@@ -561,6 +568,7 @@
 	construct_T	    construct;
 	classmember_T	    classmember;
 	storeindex_T	    storeindex;
+	lockunlock_T	    lockunlock;
     } isn_arg;
 };