diff --git a/mysql-test/r/heap_btree.result b/mysql-test/r/heap_btree.result
index fd789a39d88..a44d7333af3 100644
--- a/mysql-test/r/heap_btree.result
+++ b/mysql-test/r/heap_btree.result
@@ -280,6 +280,18 @@ a
 1
 1
 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 68aa79834fc..9484bdbce23 100644
--- a/mysql-test/t/heap_btree.test
+++ b/mysql-test/t/heap_btree.test
@@ -182,6 +182,23 @@ delete from t1 where a >= 2;
 select a from t1 order by a;
 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/storage/heap/ha_heap.cc b/storage/heap/ha_heap.cc
index f2caa7e6d18..02448eb3aa2 100644
--- a/storage/heap/ha_heap.cc
+++ b/storage/heap/ha_heap.cc
@@ -627,7 +627,10 @@ 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;