Test for BUG#6054. The bug itsel is fixed by the fix for #5837.

mysql-test/r/update.result:
  test results
mysql-test/t/update.test:
  bug test

mysql-test/r/update.result

@@ -203,3 +203,9 @@ colC	colA	colD	colE	colF
 3	4433	10005	492	500
 DROP TABLE t1;
 DROP TABLE t2;
+drop table if exists t1, t2;
+create table t1 (c1 int, c2 char(6), c3 int);
+create table t2 (c1 int, c2 char(6));
+insert into t1 values (1, "t1c2-1", 10), (2, "t1c2-2", 20);
+update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1";
+update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1" where t1.c3 = 10;

mysql-test/t/update.test

@@ -155,3 +155,12 @@ SELECT * FROM t2;
 DROP TABLE t1;
 DROP TABLE t2;
 
+#
+# Bug #6054 
+#
+drop table if exists t1, t2;
+create table t1 (c1 int, c2 char(6), c3 int);
+create table t2 (c1 int, c2 char(6));
+insert into t1 values (1, "t1c2-1", 10), (2, "t1c2-2", 20);
+update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1";
+update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1" where t1.c3 = 10;