diff --git a/mysql-test/r/explain.result b/mysql-test/r/explain.result
index 3de741b5efb..a81ff554ca2 100644
--- a/mysql-test/r/explain.result
+++ b/mysql-test/r/explain.result
@@ -155,6 +155,10 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select 1 AS `1` from (select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1`
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a INT PRIMARY KEY);
+EXPLAIN EXTENDED SELECT COUNT(a) FROM t1 USE KEY(a);
+ERROR 42000: Key 'a' doesn't exist in table 't1'
+DROP TABLE t1;
 #
 # Bug#37870: Usage of uninitialized value caused failed assertion.
 #
@@ -182,3 +186,4 @@ dt
 2001-01-01 01:01:01
 2001-01-01 01:01:01
 drop tables t1, t2;
+End of 5.1 tests.
diff --git a/mysql-test/t/explain.test b/mysql-test/t/explain.test
index 3a71fde4421..755e126baf2 100644
--- a/mysql-test/t/explain.test
+++ b/mysql-test/t/explain.test
@@ -123,6 +123,21 @@ execute s1;
 
 DROP TABLE t1,t2;
 
+
+#
+# Bug #43354: Use key hint can crash server in explain extended query
+#
+
+CREATE TABLE t1 (a INT PRIMARY KEY);
+
+--error ER_KEY_DOES_NOT_EXITS
+EXPLAIN EXTENDED SELECT COUNT(a) FROM t1 USE KEY(a);
+
+DROP TABLE t1;
+
+
+# End of 5.0 tests.
+
 --echo #
 --echo # Bug#37870: Usage of uninitialized value caused failed assertion.
 --echo #
@@ -141,4 +156,4 @@ flush tables;
 SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
 drop tables t1, t2;
 
-# End of 5.0 tests.
+--echo End of 5.1 tests.
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 1821136cc9d..a6d8bb8a52d 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -439,7 +439,8 @@ void Item_sum::make_field(Send_field *tmp_field)
 
 void Item_sum::print(String *str, enum_query_type query_type)
 {
-  Item **pargs= orig_args;
+  /* orig_args is not filled with valid values until fix_fields() */
+  Item **pargs= fixed ? orig_args : args;
   str->append(func_name());
   for (uint i=0 ; i < arg_count ; i++)
   {