diff --git a/mysql-test/r/range.result b/mysql-test/r/range.result
index e0084b53320..9b1da4ffc48 100644
--- a/mysql-test/r/range.result
+++ b/mysql-test/r/range.result
@@ -1153,3 +1153,16 @@ explain select * from t1 where dateval >= '2007-01-01 00:00:00' and dateval <= '
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	dateval	dateval	4	NULL	2	Using where
 drop table t1;
+CREATE TABLE t1 (
+a varchar(32), index (a)
+) DEFAULT CHARSET=latin1 COLLATE=latin1_bin;
+INSERT INTO t1 VALUES
+('B'), ('A'), ('A'), ('C'), ('B'), ('A'), ('A');
+SELECT a FROM t1 WHERE a='b' OR a='B';
+a
+B
+B
+EXPLAIN SELECT a FROM t1 WHERE a='b' OR a='B';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	35	NULL	3	Using where; Using index
+DROP TABLE t1;
diff --git a/mysql-test/t/range.test b/mysql-test/t/range.test
index 87ba3510326..1352b366508 100644
--- a/mysql-test/t/range.test
+++ b/mysql-test/t/range.test
@@ -955,4 +955,21 @@ explain select * from t1 where dateval >= '2007-01-01 00:00:00' and dateval <= '
 
 drop table t1;
 
+#
+# Bug #33833: different or-ed predicates were erroneously merged into one that
+# resulted in ref access instead of range access and  a wrong result set
+#
+
+CREATE TABLE t1 (
+  a varchar(32), index (a)
+) DEFAULT CHARSET=latin1 COLLATE=latin1_bin;
+
+INSERT INTO t1 VALUES
+  ('B'), ('A'), ('A'), ('C'), ('B'), ('A'), ('A');
+
+SELECT a FROM t1 WHERE a='b' OR a='B';
+EXPLAIN SELECT a FROM t1 WHERE a='b' OR a='B';
+
+DROP TABLE t1;
+
 # End of 5.0 tests
diff --git a/sql/item.cc b/sql/item.cc
index 713e7709bcb..182632bb40f 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -4302,6 +4302,49 @@ String *Item::check_well_formed_result(String *str, bool send_error)
   return str;
 }
 
+/*
+  Compare two items using a given collation
+  
+  SYNOPSIS
+    eq_by_collation()
+    item               item to compare with
+    binary_cmp         TRUE <-> compare as binaries
+    cs                 collation to use when comparing strings
+
+  DESCRIPTION
+    This method works exactly as Item::eq if the collation cs coincides with
+    the collation of the compared objects. Otherwise, first the collations that
+    differ from cs are replaced for cs and then the items are compared by
+    Item::eq. After the comparison the original collations of items are
+    restored.
+
+  RETURN
+    1    compared items has been detected as equal   
+    0    otherwise
+*/
+
+bool Item::eq_by_collation(Item *item, bool binary_cmp, CHARSET_INFO *cs)
+{
+  CHARSET_INFO *save_cs= 0;
+  CHARSET_INFO *save_item_cs= 0;
+  if (collation.collation != cs)
+  {
+    save_cs= collation.collation;
+    collation.collation= cs;
+  }
+  if (item->collation.collation != cs)
+  {
+    save_item_cs= item->collation.collation;
+    item->collation.collation= cs;
+  }
+  bool res= eq(item, binary_cmp);
+  if (save_cs)
+    collation.collation= save_cs;
+  if (save_item_cs)
+    item->collation.collation= save_item_cs;
+  return res;
+}  
+
 
 /*
   Create a field to hold a string value from an item
diff --git a/sql/item.h b/sql/item.h
index 5f511557f47..f87499f23e3 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -873,6 +873,7 @@ public:
   virtual Field::geometry_type get_geometry_type() const
     { return Field::GEOM_GEOMETRY; };
   String *check_well_formed_result(String *str, bool send_error= 0);
+  bool eq_by_collation(Item *item, bool binary_cmp, CHARSET_INFO *cs); 
 };
 
 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 87935b5548f..bdea25ab99d 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2887,7 +2887,9 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
 	  }
 	}
 	else if (old->eq_func && new_fields->eq_func &&
-		 old->val->eq(new_fields->val, old->field->binary()))
+                 old->val->eq_by_collation(new_fields->val, 
+                                           old->field->binary(),
+                                           old->field->charset()))
 
 	{
 	  old->level= and_level;