diff --git a/mysql-test/r/group_by.result b/mysql-test/r/group_by.result
index 645dd460735..f74584f6bcf 100644
--- a/mysql-test/r/group_by.result
+++ b/mysql-test/r/group_by.result
@@ -1810,4 +1810,39 @@ MAX(t2.a)
 2
 DROP TABLE t1, t2;
 #
+# Bug#55188: GROUP BY, GROUP_CONCAT and TEXT - inconsistent results
+#
+CREATE TABLE t1 (a text, b varchar(10));
+INSERT INTO t1 VALUES (repeat('1', 1300),'one'), (repeat('1', 1300),'two');
+EXPLAIN 
+SELECT SUBSTRING(a,1,10), LENGTH(a), GROUP_CONCAT(b) FROM t1 GROUP BY a;
+id	1
+select_type	SIMPLE
+table	t1
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	2
+Extra	Using filesort
+SELECT SUBSTRING(a,1,10), LENGTH(a), GROUP_CONCAT(b) FROM t1 GROUP BY a;
+SUBSTRING(a,1,10)	LENGTH(a)	GROUP_CONCAT(b)
+1111111111	1300	one,two
+EXPLAIN 
+SELECT SUBSTRING(a,1,10), LENGTH(a) FROM t1 GROUP BY a;
+id	1
+select_type	SIMPLE
+table	t1
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	2
+Extra	Using temporary; Using filesort
+SELECT SUBSTRING(a,1,10), LENGTH(a) FROM t1 GROUP BY a;
+SUBSTRING(a,1,10)	LENGTH(a)
+1111111111	1300
+DROP TABLE t1;
 # End of 5.1 tests
diff --git a/mysql-test/t/group_by.test b/mysql-test/t/group_by.test
index c5b27ee1a62..75ec1d82b02 100644
--- a/mysql-test/t/group_by.test
+++ b/mysql-test/t/group_by.test
@@ -1221,5 +1221,19 @@ DROP TABLE t1, t2;
 
 
 --echo #
+--echo # Bug#55188: GROUP BY, GROUP_CONCAT and TEXT - inconsistent results
+--echo #
+
+CREATE TABLE t1 (a text, b varchar(10));
+INSERT INTO t1 VALUES (repeat('1', 1300),'one'), (repeat('1', 1300),'two');
+
+query_vertical EXPLAIN 
+SELECT SUBSTRING(a,1,10), LENGTH(a), GROUP_CONCAT(b) FROM t1 GROUP BY a;
+SELECT SUBSTRING(a,1,10), LENGTH(a), GROUP_CONCAT(b) FROM t1 GROUP BY a;
+query_vertical EXPLAIN 
+SELECT SUBSTRING(a,1,10), LENGTH(a) FROM t1 GROUP BY a;
+SELECT SUBSTRING(a,1,10), LENGTH(a) FROM t1 GROUP BY a;
+DROP TABLE t1;
+
 
 --echo # End of 5.1 tests
diff --git a/sql/item.h b/sql/item.h
index 174995b43e6..57abb43010e 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -2740,6 +2740,7 @@ public:
 class Cached_item_str :public Cached_item
 {
   Item *item;
+  uint32 value_max_length;
   String value,tmp_value;
 public:
   Cached_item_str(THD *thd, Item *arg);
diff --git a/sql/item_buff.cc b/sql/item_buff.cc
index 2f45d0a17c2..0ac4edb3656 100644
--- a/sql/item_buff.cc
+++ b/sql/item_buff.cc
@@ -58,7 +58,9 @@ Cached_item::~Cached_item() {}
 */
 
 Cached_item_str::Cached_item_str(THD *thd, Item *arg)
-  :item(arg), value(min(arg->max_length, thd->variables.max_sort_length))
+  :item(arg),
+   value_max_length(min(arg->max_length, thd->variables.max_sort_length)),
+   value(value_max_length)
 {}
 
 bool Cached_item_str::cmp(void)
@@ -67,7 +69,7 @@ bool Cached_item_str::cmp(void)
   bool tmp;
 
   if ((res=item->val_str(&tmp_value)))
-    res->length(min(res->length(), value.alloced_length()));
+    res->length(min(res->length(), value_max_length));
   if (null_value != item->null_value)
   {
     if ((null_value= item->null_value))