diff --git a/install/inc/schema_mysql.sql b/install/inc/schema_mysql.sql
index 2fffc9635c..0fed1d359f 100644
--- a/install/inc/schema_mysql.sql
+++ b/install/inc/schema_mysql.sql
@@ -2185,7 +2185,7 @@ create index i_table_num on ca_attributes(table_num);
 create index i_element_id on ca_attributes(element_id);
 create index i_row_table_num on ca_attributes(row_id, table_num);
 create index i_prefetch ON ca_attributes(row_id, element_id, table_num);
-create index i_value_source on ca_attribute_values(value_source);
+create index i_value_source on ca_attribute_values(value_source(255));
 
 
 /*==========================================================================*/
diff --git a/support/sql/migrations/173.sql b/support/sql/migrations/173.sql
index 6b46aa5280..3f953bf8f0 100644
--- a/support/sql/migrations/173.sql
+++ b/support/sql/migrations/173.sql
@@ -7,7 +7,7 @@
 /*==========================================================================*/
 
 ALTER TABLE ca_attributes ADD COLUMN value_source varchar(1024) null default null;
-CREATE INDEX i_value_source ON ca_attributes(value_source);
+CREATE INDEX i_value_source ON ca_attributes(value_source(255));
 
 /*==========================================================================*/