diff --git a/mysql-test/r/create.result b/mysql-test/r/create.result
index 82a5ccc3e82..c75dfa9c3db 100644
--- a/mysql-test/r/create.result
+++ b/mysql-test/r/create.result
@@ -596,6 +596,13 @@ ERROR 42000: Incorrect database name 'xyz'
 create table t1(t1.name int);
 create table t2(test.t2.name int);
 drop table t1,t2;
+CREATE TABLE t1 (f1 VARCHAR(255) CHARACTER SET utf8);
+CREATE TABLE t2 AS SELECT LEFT(f1,86) AS f2 FROM t1 UNION SELECT LEFT(f1,86)
+AS f2 FROM t1;
+DESC t2;
+Field	Type	Null	Key	Default	Extra
+f2	varchar(86)	YES		NULL	
+DROP TABLE t1,t2;
 create database mysqltest;
 use mysqltest;
 drop database mysqltest;
diff --git a/mysql-test/t/create.test b/mysql-test/t/create.test
index bc281d1e027..5cd92fbc21e 100644
--- a/mysql-test/t/create.test
+++ b/mysql-test/t/create.test
@@ -503,6 +503,15 @@ create table t1(t1.name int);
 create table t2(test.t2.name int);
 drop table t1,t2;
 
+#
+# Bug #12537: UNION produces longtext instead of varchar
+#
+CREATE TABLE t1 (f1 VARCHAR(255) CHARACTER SET utf8);
+CREATE TABLE t2 AS SELECT LEFT(f1,86) AS f2 FROM t1 UNION SELECT LEFT(f1,86)
+AS f2 FROM t1;
+DESC t2;
+DROP TABLE t1,t2;
+
 #
 # Bug#11028: Crash on create table like
 #
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index d4fa5c56842..246076ac285 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -7953,6 +7953,8 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
 				   item->name, table, item->unsigned_flag);
     break;
   case STRING_RESULT:
+    DBUG_ASSERT(item->collation.collation);
+  
     enum enum_field_types type;
     /*
       DATE/TIME fields have STRING_RESULT result type. To preserve