diff --git a/mysql-test/r/create.result b/mysql-test/r/create.result
index 11c1431de7b..0a8fef8d881 100644
--- a/mysql-test/r/create.result
+++ b/mysql-test/r/create.result
@@ -447,8 +447,8 @@ t2	CREATE TABLE `t2` (
   `ifnull(c,c)` mediumint(8) default NULL,
   `ifnull(d,d)` int(11) default NULL,
   `ifnull(e,e)` bigint(20) default NULL,
-  `ifnull(f,f)` float(24,2) default NULL,
-  `ifnull(g,g)` double(53,3) default NULL,
+  `ifnull(f,f)` float(3,2) default NULL,
+  `ifnull(g,g)` double(4,3) default NULL,
   `ifnull(h,h)` decimal(5,4) default NULL,
   `ifnull(i,i)` year(4) default NULL,
   `ifnull(j,j)` date default NULL,
diff --git a/mysql-test/r/temp_table.result b/mysql-test/r/temp_table.result
index 139a7da77de..d6adf51602b 100644
--- a/mysql-test/r/temp_table.result
+++ b/mysql-test/r/temp_table.result
@@ -152,3 +152,24 @@ SELECT * FROM t1;
 i
 DROP TABLE t1;
 End of 4.1 tests.
+CREATE TABLE t1 ( c FLOAT( 20, 14 ) );
+INSERT INTO t1 VALUES( 12139 );
+CREATE TABLE t2 ( c FLOAT(30,18) );
+INSERT INTO t2 VALUES( 123456 );
+SELECT AVG( c ) FROM t1 UNION SELECT 1;
+AVG( c )
+12139
+1
+SELECT 1 UNION SELECT AVG( c ) FROM t1;
+1
+1
+12139
+SELECT 1 UNION SELECT * FROM t2 UNION SELECT 1;
+1
+1
+123456
+SELECT c/1 FROM t1 UNION SELECT 1;
+c/1
+12139
+1
+DROP TABLE t1, t2;
diff --git a/mysql-test/r/type_float.result b/mysql-test/r/type_float.result
index 0cb77f42caf..188963c5bdf 100644
--- a/mysql-test/r/type_float.result
+++ b/mysql-test/r/type_float.result
@@ -92,7 +92,7 @@ show create table t2;
 Table	Create Table
 t2	CREATE TABLE `t2` (
   `col1` double default NULL,
-  `col2` double(53,5) default NULL,
+  `col2` double(22,5) default NULL,
   `col3` double default NULL,
   `col4` double default NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
@@ -232,12 +232,12 @@ insert into t2 values ("1.23456780");
 create table t3 select * from t2 union select * from t1;
 select * from t3;
 d
-1.234567800
-100000000.000000000
+1.2345678
+100000000
 show create table t3;
 Table	Create Table
 t3	CREATE TABLE `t3` (
-  `d` double(22,9) default NULL
+  `d` double default NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1, t2, t3;
 create table t1 select  105213674794682365.00 + 0.0 x;
diff --git a/mysql-test/t/temp_table.test b/mysql-test/t/temp_table.test
index 8cb9e34ca08..90f868f5932 100644
--- a/mysql-test/t/temp_table.test
+++ b/mysql-test/t/temp_table.test
@@ -163,3 +163,19 @@ DROP TABLE t1;
 
 
 --echo End of 4.1 tests.
+
+#
+# Bug #24791: Union with AVG-groups generates wrong results
+#
+CREATE TABLE t1 ( c FLOAT( 20, 14 ) );
+INSERT INTO t1 VALUES( 12139 );
+
+CREATE TABLE t2 ( c FLOAT(30,18) );
+INSERT INTO t2 VALUES( 123456 );
+
+SELECT AVG( c ) FROM t1 UNION SELECT 1;
+SELECT 1 UNION SELECT AVG( c ) FROM t1;
+SELECT 1 UNION SELECT * FROM t2 UNION SELECT 1;
+SELECT c/1 FROM t1 UNION SELECT 1;
+
+DROP TABLE t1, t2;
diff --git a/sql/field.h b/sql/field.h
index 524380800f3..a00419893e1 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -432,6 +432,7 @@ public:
 
   int store_decimal(const my_decimal *);
   my_decimal *val_decimal(my_decimal *);
+  uint32 max_display_length() { return field_length; }
 };
 
 
@@ -461,7 +462,6 @@ public:
   void overflow(bool negative);
   bool zero_pack() const { return 0; }
   void sql_type(String &str) const;
-  uint32 max_display_length() { return field_length; }
 };
 
 
@@ -719,7 +719,6 @@ public:
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return sizeof(float); }
   void sql_type(String &str) const;
-  uint32 max_display_length() { return 24; }
 };
 
 
@@ -762,7 +761,6 @@ public:
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return sizeof(double); }
   void sql_type(String &str) const;
-  uint32 max_display_length() { return 53; }
   uint size_of() const { return sizeof(*this); }
 };
 
diff --git a/sql/item.cc b/sql/item.cc
index 11a5039ca19..958de308cc4 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -6348,8 +6348,6 @@ Item_type_holder::Item_type_holder(THD *thd, Item *item)
   :Item(thd, item), enum_set_typelib(0), fld_type(get_real_type(item))
 {
   DBUG_ASSERT(item->fixed);
-
-  max_length= display_length(item);
   maybe_null= item->maybe_null;
   collation.set(item->collation);
   get_full_info(item);
@@ -6521,11 +6519,17 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
     {
       int delta1= max_length_orig - decimals_orig;
       int delta2= item->max_length - item->decimals;
-      if (fld_type == MYSQL_TYPE_DECIMAL)
-        max_length= max(delta1, delta2) + decimals;
-      else
-        max_length= min(max(delta1, delta2) + decimals,
-                        (fld_type == MYSQL_TYPE_FLOAT) ? FLT_DIG+6 : DBL_DIG+7);
+      max_length= max(delta1, delta2) + decimals;
+      if (fld_type == MYSQL_TYPE_FLOAT && max_length > FLT_DIG + 2) 
+      {
+        max_length= FLT_DIG + 6;
+        decimals= NOT_FIXED_DEC;
+      } 
+      if (fld_type == MYSQL_TYPE_DOUBLE && max_length > DBL_DIG + 2) 
+      {
+        max_length= DBL_DIG + 7;
+        decimals= NOT_FIXED_DEC;
+      }
     }
     else
       max_length= (fld_type == MYSQL_TYPE_FLOAT) ? FLT_DIG+6 : DBL_DIG+7;
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 41f0dd6496b..acc2d22c57c 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -1096,8 +1096,10 @@ void Item_sum_avg::fix_length_and_dec()
     f_scale=  args[0]->decimals;
     dec_bin_size= my_decimal_get_binary_size(f_precision, f_scale);
   }
-  else
+  else {
     decimals= min(args[0]->decimals + prec_increment, NOT_FIXED_DEC);
+    max_length= args[0]->max_length + prec_increment;
+  }
 }