diff --git a/myisam/mi_unique.c b/myisam/mi_unique.c
index b5baa448609..1a116e50174 100644
--- a/myisam/mi_unique.c
+++ b/myisam/mi_unique.c
@@ -185,7 +185,7 @@ int mi_unique_comp(MI_UNIQUEDEF *def, const byte *a, const byte *b,
     if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT)
     {
       if (mi_compare_text(keyseg->charset, (uchar *) pos_a, length,
-                                           (uchar *) pos_b, length, 0, 0))
+                                           (uchar *) pos_b, length, 0, 1))
 	  return 1;
     }
     else
diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
index 4ceacaffcbb..0833e73b0a9 100644
--- a/mysql-test/r/ctype_utf8.result
+++ b/mysql-test/r/ctype_utf8.result
@@ -1293,3 +1293,19 @@ id	tid	val
 42749	72	VOLNÝ ADSL
 44205	72	VOLNÝ ADSL
 DROP TABLE t1;
+create table t1(a char(200) collate utf8_unicode_ci NOT NULL default '')
+default charset=utf8 collate=utf8_unicode_ci;
+insert into t1 values (unhex('65')), (unhex('C3A9')), (unhex('65'));
+explain select distinct a from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using temporary
+select distinct a from t1;
+a
+e
+explain select a from t1 group by a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using temporary; Using filesort
+select a from t1 group by a;
+a
+e
+drop table t1;
diff --git a/mysql-test/t/ctype_utf8.test b/mysql-test/t/ctype_utf8.test
index b1d485ad1ce..e737a8d381f 100644
--- a/mysql-test/t/ctype_utf8.test
+++ b/mysql-test/t/ctype_utf8.test
@@ -1040,4 +1040,18 @@ ALTER TABLE t1 ADD KEY idx (tid,val(11));
 SELECT * FROM t1 WHERE tid=72 and val LIKE 'VOLNÝ ADSL'; 
 
 DROP TABLE t1;
+
+#
+# Bug 20709: problem with utf8 fields in temporary tables
+#
+
+create table t1(a char(200) collate utf8_unicode_ci NOT NULL default '')
+  default charset=utf8 collate=utf8_unicode_ci;
+insert into t1 values (unhex('65')), (unhex('C3A9')), (unhex('65'));
+explain select distinct a from t1;
+select distinct a from t1;
+explain select a from t1 group by a;
+select a from t1 group by a;
+drop table t1;
+
 # End of 4.1 tests