diff --git a/heap/hp_create.c b/heap/hp_create.c
index 9ffa4e33108..eb7a068c78b 100644
--- a/heap/hp_create.c
+++ b/heap/hp_create.c
@@ -85,6 +85,7 @@ int heap_create(const char *name, uint keys, HP_KEYDEF *keydef,
           if (!my_binary_compare(keyinfo->seg[j].charset))
             keyinfo->flag|= HA_END_SPACE_KEY;
           keyinfo->flag|= HA_VAR_LENGTH_KEY;
+          length+= 2;
           /* Save number of bytes used to store length */
           keyinfo->seg[j].bit_start= 1;
           break;
@@ -95,6 +96,7 @@ int heap_create(const char *name, uint keys, HP_KEYDEF *keydef,
           if (!my_binary_compare(keyinfo->seg[j].charset))
             keyinfo->flag|= HA_END_SPACE_KEY;
           keyinfo->flag|= HA_VAR_LENGTH_KEY;
+          length+= 2;
           /* Save number of bytes used to store length */
           keyinfo->seg[j].bit_start= 2;
           /*
diff --git a/mysql-test/r/heap.result b/mysql-test/r/heap.result
index d72f5771f15..906c431b834 100644
--- a/mysql-test/r/heap.result
+++ b/mysql-test/r/heap.result
@@ -718,3 +718,16 @@ Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	I
 t1	MEMORY	10	Fixed	0	11	0	#	0	0	NULL	NULL	NULL	NULL	latin1_swedish_ci	NULL		
 t2	MEMORY	10	Fixed	0	12	0	#	0	0	NULL	NULL	NULL	NULL	latin1_swedish_ci	NULL		
 drop table t1, t2;
+CREATE TABLE t1(a VARCHAR(1), b VARCHAR(2), c VARCHAR(256),
+KEY(a), KEY(b), KEY(c)) ENGINE=MEMORY;
+INSERT INTO t1 VALUES('a','aa',REPEAT('a', 256)),('a','aa',REPEAT('a',256));
+SELECT COUNT(*) FROM t1 WHERE a='a';
+COUNT(*)
+2
+SELECT COUNT(*) FROM t1 WHERE b='aa';
+COUNT(*)
+2
+SELECT COUNT(*) FROM t1 WHERE c=REPEAT('a',256);
+COUNT(*)
+2
+DROP TABLE t1;
diff --git a/mysql-test/t/heap.test b/mysql-test/t/heap.test
index 82294db336d..e501fce1eeb 100644
--- a/mysql-test/t/heap.test
+++ b/mysql-test/t/heap.test
@@ -458,4 +458,16 @@ create table t2 (c varchar(10)) engine=memory;
 show table status like 't_';
 drop table t1, t2;
 
+#
+# BUG#18233 - Memory tables INDEX USING HASH (a,b) returns 1 row on
+#             SELECT WHERE a= AND b=
+#
+CREATE TABLE t1(a VARCHAR(1), b VARCHAR(2), c VARCHAR(256),
+                KEY(a), KEY(b), KEY(c)) ENGINE=MEMORY;
+INSERT INTO t1 VALUES('a','aa',REPEAT('a', 256)),('a','aa',REPEAT('a',256));
+SELECT COUNT(*) FROM t1 WHERE a='a';
+SELECT COUNT(*) FROM t1 WHERE b='aa';
+SELECT COUNT(*) FROM t1 WHERE c=REPEAT('a',256);
+DROP TABLE t1;
+
 # End of 5.0 tests