diff --git a/mysql-test/r/fulltext_left_join.result b/mysql-test/r/fulltext_left_join.result
index fdf11c14cc4..ea4cacf2fab 100644
--- a/mysql-test/r/fulltext_left_join.result
+++ b/mysql-test/r/fulltext_left_join.result
@@ -90,3 +90,10 @@ id	link	name	relevance
 1	1	string	0
 2	0	string	0
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a INT);
+CREATE TABLE t2 (b INT, c TEXT, KEY(b));
+INSERT INTO t1 VALUES(1);
+INSERT INTO t2(b,c) VALUES(2,'castle'),(3,'castle');
+SELECT * FROM t1 LEFT JOIN t2 ON a=b WHERE MATCH(c) AGAINST('+castle' IN BOOLEAN MODE);
+a	b	c
+DROP TABLE t1, t2;
diff --git a/mysql-test/t/fulltext_left_join.test b/mysql-test/t/fulltext_left_join.test
index 5942ce119ee..8c13ae5cad9 100644
--- a/mysql-test/t/fulltext_left_join.test
+++ b/mysql-test/t/fulltext_left_join.test
@@ -87,3 +87,14 @@ SELECT t1.*, MATCH(t1.name) AGAINST('string') AS relevance
 DROP TABLE t1,t2;
 
 # End of 4.1 tests
+
+#
+# BUG#25729 - boolean full text search is confused by NULLs produced by LEFT
+#             JOIN
+#
+CREATE TABLE t1 (a INT);
+CREATE TABLE t2 (b INT, c TEXT, KEY(b));
+INSERT INTO t1 VALUES(1);
+INSERT INTO t2(b,c) VALUES(2,'castle'),(3,'castle');
+SELECT * FROM t1 LEFT JOIN t2 ON a=b WHERE MATCH(c) AGAINST('+castle' IN BOOLEAN MODE);
+DROP TABLE t1, t2;
diff --git a/sql/item_func.cc b/sql/item_func.cc
index 3d92be5e9d2..f259e1319c8 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -4615,14 +4615,14 @@ void Item_func_match::init_search(bool no_order)
     fields.push_back(new Item_string(" ",1, cmp_collation.collation));
     for (uint i=1; i < arg_count; i++)
       fields.push_back(args[i]);
-    concat=new Item_func_concat_ws(fields);
+    concat_ws=new Item_func_concat_ws(fields);
     /*
       Above function used only to get value and do not need fix_fields for it:
       Item_string - basic constant
       fields - fix_fields() was already called for this arguments
       Item_func_concat_ws - do not need fix_fields() to produce value
     */
-    concat->quick_fix_field();
+    concat_ws->quick_fix_field();
   }
 
   if (master)
@@ -4837,8 +4837,8 @@ double Item_func_match::val_real()
 
   if (key == NO_SUCH_KEY)
   {
-    String *a= concat->val_str(&value);
-    if ((null_value= (a == 0)))
+    String *a= concat_ws->val_str(&value);
+    if ((null_value= (a == 0)) || !a->length())
       DBUG_RETURN(0);
     DBUG_RETURN(ft_handler->please->find_relevance(ft_handler,
 				      (byte *)a->ptr(), a->length()));
diff --git a/sql/item_func.h b/sql/item_func.h
index 68591f9c6f5..3f87d210431 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -1308,12 +1308,12 @@ public:
   FT_INFO *ft_handler;
   TABLE *table;
   Item_func_match *master;   // for master-slave optimization
-  Item *concat;              // Item_func_concat_ws
-  String value;              // value of concat
+  Item *concat_ws;           // Item_func_concat_ws
+  String value;              // value of concat_ws
   String search_value;       // key_item()'s value converted to cmp_collation
 
   Item_func_match(List<Item> &a, uint b): Item_real_func(a), key(0), flags(b),
-       join_key(0), ft_handler(0), table(0), master(0), concat(0) { }
+       join_key(0), ft_handler(0), table(0), master(0), concat_ws(0) { }
   void cleanup()
   {
     DBUG_ENTER("Item_func_match");
@@ -1321,7 +1321,7 @@ public:
     if (!master && ft_handler)
       ft_handler->please->close_search(ft_handler);
     ft_handler= 0;
-    concat= 0;
+    concat_ws= 0;
     DBUG_VOID_RETURN;
   }
   enum Functype functype() const { return FT_FUNC; }