diff --git a/heap/hp_write.c b/heap/hp_write.c
index 86e79c9d7ec..19215fcf017 100644
--- a/heap/hp_write.c
+++ b/heap/hp_write.c
@@ -105,7 +105,6 @@ int hp_rb_write_key(HP_INFO *info, HP_KEYDEF *keyinfo, const byte *record,
   heap_rb_param custom_arg;
   uint old_allocated;
 
-  info->last_pos= NULL; /* For heap_rnext/heap_rprev */
   custom_arg.keyseg= keyinfo->seg;
   custom_arg.key_length= hp_rb_make_key(keyinfo, info->recbuf, record, recpos);
   if (keyinfo->flag & HA_NOSAME)
diff --git a/mysql-test/r/heap_btree.result b/mysql-test/r/heap_btree.result
index 5b9c7f2244f..91f51a95936 100644
--- a/mysql-test/r/heap_btree.result
+++ b/mysql-test/r/heap_btree.result
@@ -280,6 +280,33 @@ a
 1
 1
 drop table t1;
+CREATE TABLE t1 (
+c1 CHAR(3),
+c2 INTEGER,
+KEY USING BTREE(c1),
+KEY USING BTREE(c2)
+) ENGINE= MEMORY;
+INSERT INTO t1 VALUES ('ABC',0), ('A',0), ('B',0), ('C',0);
+UPDATE t1 SET c2= c2 + 1 WHERE c1 = 'A';
+SELECT * FROM t1;
+c1	c2
+ABC	0
+A	1
+B	0
+C	0
+DROP TABLE t1;
+CREATE TABLE t1 (
+c1 ENUM('1', '2'),
+UNIQUE USING BTREE(c1)
+) ENGINE= MEMORY DEFAULT CHARSET= utf8;
+INSERT INTO t1 VALUES('1'), ('2');
+DROP TABLE t1;
+CREATE TABLE t1 (
+c1 SET('1', '2'),
+UNIQUE USING BTREE(c1)
+) ENGINE= MEMORY DEFAULT CHARSET= utf8;
+INSERT INTO t1 VALUES('1'), ('2');
+DROP TABLE t1;
 End of 4.1 tests
 CREATE TABLE t1(val INT, KEY USING BTREE(val)) ENGINE=memory;
 INSERT INTO t1 VALUES(0);
diff --git a/mysql-test/t/heap_btree.test b/mysql-test/t/heap_btree.test
index 03ba8661a3c..af8f9d9c9e8 100644
--- a/mysql-test/t/heap_btree.test
+++ b/mysql-test/t/heap_btree.test
@@ -182,6 +182,37 @@ delete from t1 where a >= 2;
 select a from t1 order by a;
 drop table t1;
 
+#
+# Bug#26996 - Update of a Field in a Memory Table ends with wrong result
+#
+CREATE TABLE t1 (
+  c1 CHAR(3),
+  c2 INTEGER,
+  KEY USING BTREE(c1),
+  KEY USING BTREE(c2)
+) ENGINE= MEMORY;
+INSERT INTO t1 VALUES ('ABC',0), ('A',0), ('B',0), ('C',0);
+UPDATE t1 SET c2= c2 + 1 WHERE c1 = 'A';
+SELECT * FROM t1;
+DROP TABLE t1;
+
+#
+# Bug#24985 - UTF8 ENUM primary key on MEMORY using BTREE
+#             causes incorrect duplicate entries
+#
+CREATE TABLE t1 (
+  c1 ENUM('1', '2'),
+  UNIQUE USING BTREE(c1)
+) ENGINE= MEMORY DEFAULT CHARSET= utf8;
+INSERT INTO t1 VALUES('1'), ('2');
+DROP TABLE t1;
+CREATE TABLE t1 (
+  c1 SET('1', '2'),
+  UNIQUE USING BTREE(c1)
+) ENGINE= MEMORY DEFAULT CHARSET= utf8;
+INSERT INTO t1 VALUES('1'), ('2');
+DROP TABLE t1;
+
 --echo End of 4.1 tests
 
 #
diff --git a/sql/ha_heap.cc b/sql/ha_heap.cc
index d1a931b07f2..8838aa99c1a 100644
--- a/sql/ha_heap.cc
+++ b/sql/ha_heap.cc
@@ -604,7 +604,10 @@ int ha_heap::create(const char *name, TABLE *table_arg,
       seg->length=  (uint) key_part->length;
       seg->flag=    key_part->key_part_flag;
 
-      seg->charset= field->charset();
+      if (field->flags & (ENUM_FLAG | SET_FLAG))
+        seg->charset= &my_charset_bin;
+      else
+        seg->charset= field->charset();
       if (field->null_ptr)
       {
 	seg->null_bit= field->null_bit;
diff --git a/sql/ha_myisam.cc b/sql/ha_myisam.cc
index 10d3dbb2ec5..6d8a770175d 100644
--- a/sql/ha_myisam.cc
+++ b/sql/ha_myisam.cc
@@ -976,6 +976,22 @@ int ha_myisam::repair(THD *thd, MI_CHECK &param, bool do_optimize)
   ha_rows rows= file->state->records;
   DBUG_ENTER("ha_myisam::repair");
 
+  /*
+    Normally this method is entered with a properly opened table. If the
+    repair fails, it can be repeated with more elaborate options. Under
+    special circumstances it can happen that a repair fails so that it
+    closed the data file and cannot re-open it. In this case file->dfile
+    is set to -1. We must not try another repair without an open data
+    file. (Bug #25289)
+  */
+  if (file->dfile == -1)
+  {
+    sql_print_information("Retrying repair of: '%s' failed. "
+                          "Please try REPAIR EXTENDED or myisamchk",
+                          table->s->path);
+    DBUG_RETURN(HA_ADMIN_FAILED);
+  }
+
   param.db_name=    table->s->db;
   param.table_name= table->alias;
   param.tmpfile_createflag = O_RDWR | O_TRUNC;