diff --git a/mysql-test/include/mix1.inc b/mysql-test/include/mix1.inc
index c032aaea50e..221c114cd95 100644
--- a/mysql-test/include/mix1.inc
+++ b/mysql-test/include/mix1.inc
@@ -814,8 +814,16 @@ create table t1 (a int) engine=innodb;
 alter table t1 alter a set default 1;
 drop table t1;
 
---echo End of 5.0 tests
+#
+# Bug #28125: ERROR 2013 when adding index.
+#
+create table t1(a text) engine=innodb default charset=utf8; 
+insert into t1 values('aaa');
+alter table t1 add index(a(1024));
+show create table t1;
+drop table t1;
 
+--echo End of 5.0 tests
 
 # Fix for BUG#19243 "wrong LAST_INSERT_ID() after ON DUPLICATE KEY
 # UPDATE": if the row is updated, it's like a regular UPDATE:
@@ -917,5 +925,4 @@ unlock tables;
 select * from t1;
 drop tables t1;
 
-
 --echo End of 5.1 tests
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index c603f1ad77f..70bd549612c 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -2789,6 +2789,8 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
 			  length);
 	      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
 			   ER_TOO_LONG_KEY, warn_buff);
+              /* Align key length to multibyte char boundary */
+              length-= length % sql_field->charset->mbmaxlen;
 	    }
 	    else
 	    {
@@ -2819,8 +2821,6 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
       if (length > file->max_key_part_length() && key->type != Key::FULLTEXT)
       {
         length= file->max_key_part_length();
-        /* Align key length to multibyte char boundary */
-        length-= length % sql_field->charset->mbmaxlen;
 	if (key->type == Key::MULTIPLE)
 	{
 	  /* not a critical problem */
@@ -2829,6 +2829,8 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
 		      length);
 	  push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
 		       ER_TOO_LONG_KEY, warn_buff);
+          /* Align key length to multibyte char boundary */
+          length-= length % sql_field->charset->mbmaxlen;
 	}
 	else
 	{