diff --git a/mysql-test/r/heap_btree.result b/mysql-test/r/heap_btree.result
index 7a0e46a2a1c..91f51a95936 100644
--- a/mysql-test/r/heap_btree.result
+++ b/mysql-test/r/heap_btree.result
@@ -295,6 +295,18 @@ 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 2dd5f64014a..af8f9d9c9e8 100644
--- a/mysql-test/t/heap_btree.test
+++ b/mysql-test/t/heap_btree.test
@@ -196,6 +196,23 @@ 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;