diff --git a/mysql-test/r/sp-bugs.result b/mysql-test/r/sp-bugs.result
index 14c5311bbe5..38ddab52b8a 100644
--- a/mysql-test/r/sp-bugs.result
+++ b/mysql-test/r/sp-bugs.result
@@ -44,4 +44,19 @@ SELECT f2 ();
 f2 ()
 NULL
 DROP SCHEMA testdb;
+USE test;
+#
+# Bug#50423: Crash on second call of a procedure dropping a trigger
+#
+DROP TABLE IF EXISTS t1;
+DROP TRIGGER IF EXISTS tr1;
+DROP PROCEDURE IF EXISTS p1;
+CREATE TABLE t1 (f1 INTEGER);
+CREATE TRIGGER tr1 BEFORE INSERT ON t1 FOR EACH ROW SET @aux = 1;
+CREATE PROCEDURE p1 () DROP TRIGGER tr1;
+CALL p1 ();
+CALL p1 ();
+ERROR HY000: Trigger does not exist
+DROP TABLE t1;
+DROP PROCEDURE p1;
 End of 5.1 tests
diff --git a/mysql-test/t/sp-bugs.test b/mysql-test/t/sp-bugs.test
index 7b94e65a5e9..1eb283f7874 100644
--- a/mysql-test/t/sp-bugs.test
+++ b/mysql-test/t/sp-bugs.test
@@ -57,5 +57,27 @@ SELECT f2 ();
 
 DROP SCHEMA testdb;
 
+USE test;
+
+--echo #
+--echo # Bug#50423: Crash on second call of a procedure dropping a trigger
+--echo #
+
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+DROP TRIGGER IF EXISTS tr1;
+DROP PROCEDURE IF EXISTS p1;
+--enable_warnings
+
+CREATE TABLE t1 (f1 INTEGER);
+CREATE TRIGGER tr1 BEFORE INSERT ON t1 FOR EACH ROW SET @aux = 1;
+CREATE PROCEDURE p1 () DROP TRIGGER tr1;
+
+CALL p1 ();
+--error ER_TRG_DOES_NOT_EXIST
+CALL p1 ();
+
+DROP TABLE t1;
+DROP PROCEDURE p1;
 
 --echo End of 5.1 tests
diff --git a/sql/sql_trigger.cc b/sql/sql_trigger.cc
index ba0515d38ad..aafb25013f6 100644
--- a/sql/sql_trigger.cc
+++ b/sql/sql_trigger.cc
@@ -327,6 +327,7 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   TABLE *table;
   bool result= TRUE;
   String stmt_query;
+  Query_tables_list backup;
   bool need_start_waiting= FALSE;
 
   DBUG_ENTER("mysql_create_or_drop_trigger");
@@ -393,6 +394,12 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   {
     bool if_exists= thd->lex->drop_if_exists;
 
+    /*
+      Protect the query table list from the temporary and potentially
+      destructive changes necessary to open the trigger's table.
+    */
+    thd->lex->reset_n_backup_query_tables_list(&backup);
+
     if (add_table_for_trigger(thd, thd->lex->spname, if_exists, & tables))
       goto end;
 
@@ -512,6 +519,10 @@ end:
 
   VOID(pthread_mutex_unlock(&LOCK_open));
 
+  /* Restore the query table list. Used only for drop trigger. */
+  if (!create)
+    thd->lex->restore_backup_query_tables_list(&backup);
+
   if (need_start_waiting)
     start_waiting_global_read_lock(thd);
 
@@ -1625,10 +1636,6 @@ bool add_table_for_trigger(THD *thd,
   if (load_table_name_for_trigger(thd, trg_name, &trn_path, &tbl_name))
     DBUG_RETURN(TRUE);
 
-  /* We need to reset statement table list to be PS/SP friendly. */
-  lex->query_tables= 0;
-  lex->query_tables_last= &lex->query_tables;
-
   *table= sp_add_to_query_tables(thd, lex, trg_name->m_db.str,
                                  tbl_name.str, TL_IGNORE);