diff --git a/qse/include/qse/xli/xli.h b/qse/include/qse/xli/xli.h
index e202240e..4fcbbe18 100644
--- a/qse/include/qse/xli/xli.h
+++ b/qse/include/qse/xli/xli.h
@@ -454,9 +454,15 @@ typedef void (*qse_xli_pair_read_cb_t) (
 	qse_xli_loc_t*  loc
 );
 
+typedef int (*qse_xli_pair_writable_cb_t) (
+	qse_xli_t*      xli,
+	qse_xli_pair_t* pair
+);
+
 struct qse_xli_cbs_t
 {
 	qse_xli_pair_read_cb_t pair_read;
+	qse_xli_pair_writable_cb_t pair_writable;
 };
 typedef struct qse_xli_cbs_t qse_xli_cbs_t;
 
diff --git a/qse/lib/xli/write-ini.c b/qse/lib/xli/write-ini.c
index 5a1cb973..e59b3219 100644
--- a/qse/lib/xli/write-ini.c
+++ b/qse/lib/xli/write-ini.c
@@ -54,6 +54,8 @@ static int write_list (qse_xli_t* xli, qse_xli_list_t* list, int depth)
 			{
 				qse_xli_pair_t* pair = (qse_xli_pair_t*)curatom;
 
+				if (xli->opt.cbs.pair_writable && !xli->opt.cbs.pair_writable(xli, pair)) continue;
+
 				if (pair->tag)
 				{
 					/* the tag can't be written. so ignore it */
diff --git a/qse/lib/xli/write-json.c b/qse/lib/xli/write-json.c
index 5b5c221c..8ae3232e 100644
--- a/qse/lib/xli/write-json.c
+++ b/qse/lib/xli/write-json.c
@@ -106,6 +106,8 @@ static int write_list (qse_xli_t* xli, qse_xli_list_t* list, int depth)
 			{
 				qse_xli_pair_t* pair = (qse_xli_pair_t*)curatom;
 
+				if (xli->opt.cbs.pair_writable && !xli->opt.cbs.pair_writable(xli, pair)) continue;
+
 				if (write_indentation(xli, depth) <= -1) return -1;
 
 				if (!(list->flags & QSE_XLI_LIST_ARRAYED))
@@ -130,15 +132,15 @@ static int write_list (qse_xli_t* xli, qse_xli_list_t* list, int depth)
 				switch (pair->val->type)
 				{
 					case QSE_XLI_NIL:
-						if (write_to_current_stream(xli, QSE_T("nil"), 5, 0) <= -1) return -1;
+						if (write_to_current_stream(xli, QSE_T("nil"), 3, 0) <= -1) return -1;
 						break;
 
 					case QSE_XLI_TRUE:
-						if (write_to_current_stream(xli, QSE_T("true"), 6, 0) <= -1) return -1;
+						if (write_to_current_stream(xli, QSE_T("true"), 4, 0) <= -1) return -1;
 						break;
 
 					case QSE_XLI_FALSE:
-						if (write_to_current_stream(xli, QSE_T("false"), 7, 0) <= -1) return -1;
+						if (write_to_current_stream(xli, QSE_T("false"), 5, 0) <= -1) return -1;
 						break;
 
 					case QSE_XLI_STR:
diff --git a/qse/lib/xli/write.c b/qse/lib/xli/write.c
index 0d361ac4..e06c563f 100644
--- a/qse/lib/xli/write.c
+++ b/qse/lib/xli/write.c
@@ -267,7 +267,9 @@ static int write_list (qse_xli_t* xli, qse_xli_list_t* list, int depth)
 			case QSE_XLI_PAIR:
 			{
 				qse_xli_pair_t* pair = (qse_xli_pair_t*)curatom;
-				
+
+				if (xli->opt.cbs.pair_writable && !xli->opt.cbs.pair_writable(xli, pair)) continue;
+
 				if (write_indentation (xli, depth) <= -1) return -1;
 
 				if (pair->tag)