diff --git a/mysql-test/r/join.result b/mysql-test/r/join.result
index 2585bf7a26e..beba47cd39b 100644
--- a/mysql-test/r/join.result
+++ b/mysql-test/r/join.result
@@ -942,4 +942,14 @@ ROW(t1.b, 1111.11) <=> ROW('','');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 DROP TABLE t1;
+#
+# Bug #50335: Assertion `!(order->used & map)' in eq_ref_table
+# 
+CREATE TABLE t1 (a INT NOT NULL, b INT NOT NULL, PRIMARY KEY (a,b));
+INSERT INTO t1 VALUES (0,0), (1,1);
+SELECT * FROM t1 STRAIGHT_JOIN t1 t2 ON t1.a=t2.a AND t1.a=t2.b ORDER BY t2.a, t1.a;
+a	b	a	b
+0	0	0	0
+1	1	1	1
+DROP TABLE t1;
 End of 5.0 tests.
diff --git a/mysql-test/t/join.test b/mysql-test/t/join.test
index a9900c34f1e..d51740bb380 100644
--- a/mysql-test/t/join.test
+++ b/mysql-test/t/join.test
@@ -736,4 +736,15 @@ WHERE ROW(t1.a, 1111.11) = ROW(1111.11, 1111.11) AND
 ROW(t1.b, 1111.11) <=> ROW('','');
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #50335: Assertion `!(order->used & map)' in eq_ref_table
+--echo # 
+
+CREATE TABLE t1 (a INT NOT NULL, b INT NOT NULL, PRIMARY KEY (a,b));
+INSERT INTO t1 VALUES (0,0), (1,1);
+
+SELECT * FROM t1 STRAIGHT_JOIN t1 t2 ON t1.a=t2.a AND t1.a=t2.b ORDER BY t2.a, t1.a;
+
+DROP TABLE t1;
+
 --echo End of 5.0 tests.
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 84de1fe241b..f0177893840 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -6720,9 +6720,11 @@ eq_ref_table(JOIN *join, ORDER *start_order, JOIN_TAB *tab)
       }
       if (order)
       {
-	found++;
-	DBUG_ASSERT(!(order->used & map));
-	order->used|=map;
+        if (!(order->used & map))
+        {
+          found++;
+          order->used|= map;
+        }
 	continue;				// Used in ORDER BY
       }
       if (!only_eq_ref_tables(join,start_order, (*ref_item)->used_tables()))