diff --git a/mysql-test/r/heap_btree.result b/mysql-test/r/heap_btree.result
index e6492e90b80..512a8a52845 100644
--- a/mysql-test/r/heap_btree.result
+++ b/mysql-test/r/heap_btree.result
@@ -280,4 +280,16 @@ 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
diff --git a/mysql-test/t/heap_btree.test b/mysql-test/t/heap_btree.test
index 9aa820becd9..eb4672473f6 100644
--- a/mysql-test/t/heap_btree.test
+++ b/mysql-test/t/heap_btree.test
@@ -182,4 +182,21 @@ 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/sql/ha_heap.cc b/sql/ha_heap.cc
index 3e981087df7..dd3a84aaaee 100644
--- a/sql/ha_heap.cc
+++ b/sql/ha_heap.cc
@@ -549,7 +549,10 @@ int ha_heap::create(const char *name, TABLE *table_arg,
       seg->start=   (uint) key_part->offset;
       seg->length=  (uint) key_part->length;
       seg->flag =   0;
-      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;