diff --git a/mysql-test/r/create.result b/mysql-test/r/create.result
index 4cb57a43cf3..d9eccbcf27e 100644
--- a/mysql-test/r/create.result
+++ b/mysql-test/r/create.result
@@ -468,3 +468,44 @@ NULL
 select database();
 database()
 NULL
+use test;
+create table t1 (a int, index `primary` (a));
+ERROR 42000: Incorrect index name 'primary'
+create table t1 (a int, index `PRIMARY` (a));
+ERROR 42000: Incorrect index name 'PRIMARY'
+create table t1 (`primary` int, index(`primary`));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `primary` int(11) default NULL,
+  KEY `primary_2` (`primary`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create table t2 (`PRIMARY` int, index(`PRIMARY`));
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `PRIMARY` int(11) default NULL,
+  KEY `PRIMARY_2` (`PRIMARY`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create table t3 (a int);
+alter table t3 add index `primary` (a);
+ERROR 42000: Incorrect index name 'primary'
+alter table t3 add index `PRIMARY` (a);
+ERROR 42000: Incorrect index name 'PRIMARY'
+create table t4 (`primary` int);
+alter table t4 add index(`primary`);
+show create table t4;
+Table	Create Table
+t4	CREATE TABLE `t4` (
+  `primary` int(11) default NULL,
+  KEY `primary_2` (`primary`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create table t5 (`PRIMARY` int);
+alter table t5 add index(`PRIMARY`);
+show create table t5;
+Table	Create Table
+t5	CREATE TABLE `t5` (
+  `PRIMARY` int(11) default NULL,
+  KEY `PRIMARY_2` (`PRIMARY`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1, t2, t3, t4, t5;
diff --git a/mysql-test/t/create.test b/mysql-test/t/create.test
index 70fa4173c76..fedd82356f9 100644
--- a/mysql-test/t/create.test
+++ b/mysql-test/t/create.test
@@ -359,3 +359,33 @@ select database();
 # Connect without a database
 connect (user4,localhost,mysqltest_1,,*NO-ONE*);
 select database();
+
+#
+# Test for Bug 856 'Naming a key "Primary" causes trouble'
+#
+
+use test;
+--error 1280
+create table t1 (a int, index `primary` (a));
+--error 1280
+create table t1 (a int, index `PRIMARY` (a));
+
+create table t1 (`primary` int, index(`primary`));
+show create table t1;
+create table t2 (`PRIMARY` int, index(`PRIMARY`));
+show create table t2;
+
+create table t3 (a int);
+--error 1280
+alter table t3 add index `primary` (a);
+--error 1280
+alter table t3 add index `PRIMARY` (a);
+
+create table t4 (`primary` int);
+alter table t4 add index(`primary`);
+show create table t4;
+create table t5 (`PRIMARY` int);
+alter table t5 add index(`PRIMARY`);
+show create table t5;
+
+drop table t1, t2, t3, t4, t5;
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index ee11b7b9da0..200511481b1 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -639,6 +639,12 @@ int mysql_create_table(THD *thd,const char *db, const char *table_name,
       DBUG_RETURN(-1);
     }
     key_parts+=key->columns.elements;
+    if (key->name && !tmp_table &&
+	!my_strcasecmp(system_charset_info,key->name,primary_key_name))
+    {
+      my_error(ER_WRONG_NAME_FOR_INDEX, MYF(0), key->name);
+      DBUG_RETURN(-1);
+    }
   }
   tmp=min(file->max_keys(), MAX_KEY);
   if (key_count > tmp)
@@ -1079,7 +1085,8 @@ make_unique_key_name(const char *field_name,KEY *start,KEY *end)
 {
   char buff[MAX_FIELD_NAME],*buff_end;
 
-  if (!check_if_keyname_exists(field_name,start,end))
+  if (!check_if_keyname_exists(field_name,start,end) &&
+      my_strcasecmp(system_charset_info,field_name,primary_key_name))
     return (char*) field_name;			// Use fieldname
   buff_end=strmake(buff,field_name,MAX_FIELD_NAME-4);
   for (uint i=2 ; ; i++)
@@ -2403,6 +2410,12 @@ int mysql_alter_table(THD *thd,char *new_db, char *new_name,
     {
       if (key->type != Key::FOREIGN_KEY)
 	key_list.push_back(key);
+      if (key->name &&
+	  !my_strcasecmp(system_charset_info,key->name,primary_key_name))
+      {
+	my_error(ER_WRONG_NAME_FOR_INDEX, MYF(0), key->name);
+	DBUG_RETURN(-1);
+      }
     }
   }