diff --git a/mysql-test/r/join.result b/mysql-test/r/join.result
index 96504df4b1e..dae3d16c781 100644
--- a/mysql-test/r/join.result
+++ b/mysql-test/r/join.result
@@ -1,4 +1,5 @@
 drop table if exists t1,t2,t3;
+drop view if exists v1,v2;
 CREATE TABLE t1 (S1 INT);
 CREATE TABLE t2 (S1 INT);
 INSERT INTO t1 VALUES (1);
@@ -1220,4 +1221,22 @@ f1
 2
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
+#
+# Bug LP:798597: Incorrect "Duplicate entry" error with views and
+#                GROUP BY
+#
+CREATE TABLE t1 ( f1 int NOT NULL , f2 int NOT NULL ) ;
+INSERT INTO t1 VALUES (214,0),(6,6);
+CREATE TABLE t2 ( f2 int) ;
+INSERT INTO t2 VALUES (88),(88);
+CREATE ALGORITHM=MERGE VIEW v1 AS SELECT t1.f1, t2.f2 FROM (t2 LEFT JOIN t1 ON (t2.f2 <> t1.f1)) WHERE (t1.f2 <= 0) ;
+CREATE ALGORITHM=MERGE VIEW v2 AS SELECT t1.f1, t2.f2 FROM (t2 LEFT JOIN t1 ON (t2.f2 <> t1.f1)) WHERE (t1.f2 <= 0 or t1.f2 is null) ;
+SELECT f1 , MIN(f2) FROM v1 GROUP BY f1;
+f1	MIN(f2)
+214	88
+SELECT f1 , MIN(f2) FROM v2 GROUP BY f1;
+f1	MIN(f2)
+214	88
+drop table t1,t2;
+drop view v1,v2;
 End of 5.1 tests
diff --git a/mysql-test/t/join.test b/mysql-test/t/join.test
index 05d630edfb2..0a573e7cd4f 100644
--- a/mysql-test/t/join.test
+++ b/mysql-test/t/join.test
@@ -2,6 +2,7 @@
 # Initialization
 --disable_warnings
 drop table if exists t1,t2,t3;
+drop view if exists v1,v2;
 --enable_warnings
 
 #
@@ -921,4 +922,21 @@ EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug LP:798597: Incorrect "Duplicate entry" error with views and
+--echo #                GROUP BY
+--echo #
+
+CREATE TABLE t1 ( f1 int NOT NULL , f2 int NOT NULL ) ;
+INSERT INTO t1 VALUES (214,0),(6,6);
+CREATE TABLE t2 ( f2 int) ;
+INSERT INTO t2 VALUES (88),(88);
+CREATE ALGORITHM=MERGE VIEW v1 AS SELECT t1.f1, t2.f2 FROM (t2 LEFT JOIN t1 ON (t2.f2 <> t1.f1)) WHERE (t1.f2 <= 0) ;
+CREATE ALGORITHM=MERGE VIEW v2 AS SELECT t1.f1, t2.f2 FROM (t2 LEFT JOIN t1 ON (t2.f2 <> t1.f1)) WHERE (t1.f2 <= 0 or t1.f2 is null) ;
+SELECT f1 , MIN(f2) FROM v1 GROUP BY f1;
+SELECT f1 , MIN(f2) FROM v2 GROUP BY f1;
+drop table t1,t2;
+drop view v1,v2;
+
+
 --echo End of 5.1 tests
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 91fc95a2909..0bd4e8ae647 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -10637,15 +10637,30 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
 	 (ha_base_keytype) key_part_info->type == HA_KEYTYPE_VARTEXT1 ||
 	 (ha_base_keytype) key_part_info->type == HA_KEYTYPE_VARTEXT2) ?
 	0 : FIELDFLAG_BINARY;
+
       if (!using_unique_constraint)
       {
 	cur_group->buff=(char*) group_buff;
+
+        if (maybe_null & !field->null_bit)
+        {
+          /*
+            This can only happen in the unusual case where an outer join
+            table was found to be not-nullable by the optimizer and we
+            the item can't really be null.
+            We solve this by marking the item as !maybe_null to ensure
+            that the key,field and item definition match.
+          */
+          (*cur_group->item)->maybe_null= maybe_null= 0;
+        }
+
 	if (!(cur_group->field= field->new_key_field(thd->mem_root,table,
                                                      group_buff +
                                                      test(maybe_null),
                                                      field->null_ptr,
                                                      field->null_bit)))
 	  goto err; /* purecov: inspected */
+
 	if (maybe_null)
 	{
 	  /*
@@ -10667,6 +10682,12 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
       }
       keyinfo->key_length+=  key_part_info->length;
     }
+    /*
+      Ensure we didn't overrun the group buffer. The < is only true when
+      some maybe_null fields was changed to be not null fields.
+    */
+    DBUG_ASSERT(using_unique_constraint ||
+                group_buff <= param->group_buff + param->group_length);
   }
 
   if (distinct && field_count != param->hidden_field_count)