diff --git a/mysql-test/r/func_gconcat.result b/mysql-test/r/func_gconcat.result
index 19b5f03de6b..77d11831842 100644
--- a/mysql-test/r/func_gconcat.result
+++ b/mysql-test/r/func_gconcat.result
@@ -931,4 +931,19 @@ SELECT GROUP_CONCAT(DISTINCT b, a ORDER BY b) FROM t1;
 GROUP_CONCAT(DISTINCT b, a ORDER BY b)
 11,22,32
 DROP TABLE t1, t2, t3;
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (),();
+SELECT s1.d1 FROM
+(
+SELECT
+t1.a as d1,
+GROUP_CONCAT(DISTINCT t1.a) AS d2
+FROM
+t1 AS t1,
+t1 AS t2
+GROUP BY 1
+) AS s1;
+d1
+NULL
+DROP TABLE t1;
 End of 5.0 tests
diff --git a/mysql-test/t/func_gconcat.test b/mysql-test/t/func_gconcat.test
index 84c286e516b..87632fbdbb8 100644
--- a/mysql-test/t/func_gconcat.test
+++ b/mysql-test/t/func_gconcat.test
@@ -640,4 +640,21 @@ SELECT GROUP_CONCAT(DISTINCT b, a ORDER BY b) FROM t1;
 
 DROP TABLE t1, t2, t3;
 
+#
+# Bug #34747: crash in debug assertion check after derived table
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (),();
+SELECT s1.d1 FROM
+(
+ SELECT
+  t1.a as d1,
+  GROUP_CONCAT(DISTINCT t1.a) AS d2
+ FROM
+  t1 AS t1,
+  t1 AS t2
+ GROUP BY 1
+) AS s1;
+DROP TABLE t1;
+
 --echo End of 5.0 tests
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 47a7073c2e7..3d6d46ab3f4 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -3460,6 +3460,6 @@ void Item_func_group_concat::print(String *str)
 
 Item_func_group_concat::~Item_func_group_concat()
 {
-  if (unique_filter) 
+  if (!original && unique_filter)
     delete unique_filter;    
 }