diff --git a/mysql-test/r/ctype_ucs.result b/mysql-test/r/ctype_ucs.result
index fef13b19ae8..72fd5cac639 100644
--- a/mysql-test/r/ctype_ucs.result
+++ b/mysql-test/r/ctype_ucs.result
@@ -803,6 +803,14 @@ quote(name)
 ????????
 ????????????????
 drop table bug20536;
+set names ucs2;
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
+set names ucs2 collate ucs2_bin;
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
+set character_set_client= ucs2;
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
+set character_set_client= concat('ucs', substr('2', 1));
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
 CREATE TABLE t1(a TEXT CHARSET ucs2 COLLATE ucs2_unicode_ci);
 INSERT INTO t1 VALUES('abcd');
 SELECT * FROM t1 WHERE MATCH(a) AGAINST ('+abcd' IN BOOLEAN MODE);
diff --git a/mysql-test/r/ps.result b/mysql-test/r/ps.result
index 49e4bf2f318..49643dd3f78 100644
--- a/mysql-test/r/ps.result
+++ b/mysql-test/r/ps.result
@@ -1109,4 +1109,9 @@ a
 13
 DEALLOCATE PREPARE st1;
 DROP TABLE t1;
+create table t1 (a int, b tinyint);
+prepare st1 from 'update t1 set b= (str_to_date(a, a))';
+execute st1;
+deallocate prepare st1;
+drop table t1;
 End of 4.1 tests.
diff --git a/mysql-test/t/ctype_ucs.test b/mysql-test/t/ctype_ucs.test
index 57f741597e0..81bc39553e9 100644
--- a/mysql-test/t/ctype_ucs.test
+++ b/mysql-test/t/ctype_ucs.test
@@ -535,6 +535,18 @@ select quote(name) from bug20536;
 
 drop table bug20536;
 
+#
+# Bug #31615: crash after set names ucs2 collate xxx
+#
+--error 1231
+set names ucs2;
+--error 1231
+set names ucs2 collate ucs2_bin;
+--error 1231
+set character_set_client= ucs2;
+--error 1231
+set character_set_client= concat('ucs', substr('2', 1));
+
 #
 # BUG#31159 - fulltext search on ucs2 column crashes server
 #
diff --git a/mysql-test/t/ps.test b/mysql-test/t/ps.test
index 5e5dcc36b19..18beb357d05 100644
--- a/mysql-test/t/ps.test
+++ b/mysql-test/t/ps.test
@@ -1146,4 +1146,13 @@ EXECUTE st1;
 DEALLOCATE PREPARE st1;
 DROP TABLE t1;
 
+#
+# Bug #32137: prepared statement crash with str_to_date in update clause
+#
+create table t1 (a int, b tinyint);
+prepare st1 from 'update t1 set b= (str_to_date(a, a))';
+execute st1;
+deallocate prepare st1;
+drop table t1;
+
 --echo End of 4.1 tests.
diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index 4bd3d68b9c1..08e0a727544 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -2958,39 +2958,42 @@ Field *Item_func_str_to_date::tmp_table_field(TABLE *t_arg)
 
 void Item_func_str_to_date::fix_length_and_dec()
 {
-  char format_buff[64];
-  String format_str(format_buff, sizeof(format_buff), &my_charset_bin);
-  String *format;
   maybe_null= 1;
   decimals=0;
   cached_field_type= MYSQL_TYPE_STRING;
   max_length= MAX_DATETIME_FULL_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
   cached_timestamp_type= MYSQL_TIMESTAMP_NONE;
-  format= args[1]->val_str(&format_str);
-  if (!args[1]->null_value && (const_item= args[1]->const_item()))
+  if ((const_item= args[1]->const_item()))
   {
-    cached_format_type= get_date_time_result_type(format->ptr(),
-                                                  format->length());
-    switch (cached_format_type) {
-    case DATE_ONLY:
-      cached_timestamp_type= MYSQL_TIMESTAMP_DATE;
-      cached_field_type= MYSQL_TYPE_DATE; 
-      max_length= MAX_DATE_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
-      break;
-    case TIME_ONLY:
-    case TIME_MICROSECOND:
-      cached_timestamp_type= MYSQL_TIMESTAMP_TIME;
-      cached_field_type= MYSQL_TYPE_TIME; 
-      max_length= MAX_TIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
-      break;
-    default:
-      cached_timestamp_type= MYSQL_TIMESTAMP_DATETIME;
-      cached_field_type= MYSQL_TYPE_DATETIME; 
-      break;
+    char format_buff[64];
+    String format_str(format_buff, sizeof(format_buff), &my_charset_bin);
+    String *format= args[1]->val_str(&format_str);
+    if (!args[1]->null_value)
+    {
+      cached_format_type= get_date_time_result_type(format->ptr(),
+                                                    format->length());
+      switch (cached_format_type) {
+      case DATE_ONLY:
+        cached_timestamp_type= MYSQL_TIMESTAMP_DATE;
+        cached_field_type= MYSQL_TYPE_DATE; 
+        max_length= MAX_DATE_WIDTH * MY_CHARSET_BIN_MB_MAXLEN;
+        break;
+      case TIME_ONLY:
+      case TIME_MICROSECOND:
+        cached_timestamp_type= MYSQL_TIMESTAMP_TIME;
+        cached_field_type= MYSQL_TYPE_TIME; 
+        max_length= MAX_TIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN;
+        break;
+      default:
+        cached_timestamp_type= MYSQL_TIMESTAMP_DATETIME;
+        cached_field_type= MYSQL_TYPE_DATETIME; 
+        break;
+      }
     }
   }
 }
 
+
 bool Item_func_str_to_date::get_date(TIME *ltime, uint fuzzy_date)
 {
   DATE_TIME_FORMAT date_time_format;
diff --git a/sql/set_var.cc b/sql/set_var.cc
index 1d18eba30a8..25af4cf5c9e 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -1992,6 +1992,21 @@ void sys_var_character_set_client::set_default(THD *thd, enum_var_type type)
 }
 
 
+bool sys_var_character_set_client::check(THD *thd, set_var *var)
+{
+  if (sys_var_character_set::check(thd, var))
+    return 1;
+  /* Currently, UCS-2 cannot be used as a client character set */
+  if (var->save_result.charset->mbminlen > 1)
+  {
+    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), name, 
+             var->save_result.charset->csname); 
+    return 1;
+  }
+  return 0;
+}
+
+
 CHARSET_INFO **
 sys_var_character_set_results::ci_ptr(THD *thd, enum_var_type type)
 {
@@ -2355,6 +2370,13 @@ end:
 
 int set_var_collation_client::check(THD *thd)
 {
+  /* Currently, UCS-2 cannot be used as a client character set */
+  if (character_set_client->mbminlen > 1)
+  {
+    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), "character_set_client",
+             character_set_client->csname);
+    return 1;
+  }
   return 0;
 }
 
diff --git a/sql/set_var.h b/sql/set_var.h
index 78b34963e9d..f6fd0a082b5 100644
--- a/sql/set_var.h
+++ b/sql/set_var.h
@@ -578,6 +578,7 @@ public:
     sys_var_character_set(name_arg) {}
   void set_default(THD *thd, enum_var_type type);
   CHARSET_INFO **ci_ptr(THD *thd, enum_var_type type);
+  bool check(THD *thd, set_var *var);
 };
 
 class sys_var_character_set_results :public sys_var_character_set