diff --git a/mysql-test/suite/binlog/r/binlog_format_switch_in_tmp_table.result b/mysql-test/suite/binlog/r/binlog_format_switch_in_tmp_table.result
new file mode 100644
index 00000000000..f886ccb134d
--- /dev/null
+++ b/mysql-test/suite/binlog/r/binlog_format_switch_in_tmp_table.result
@@ -0,0 +1,78 @@
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+MIXED
+CREATE TABLE t1 (a VARCHAR(100));
+CREATE TEMPORARY TABLE t2 (a VARCHAR(100));
+# Test allow switching @@SESSION.binlog_format from MIXED to STATEMENT
+# when there are open temp tables and we are logging in statement based format.
+SET SESSION binlog_format = STATEMENT;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+STATEMENT
+# Test allow switching @@SESSION.binlog_format from STATEMENT to
+# STATEMENT when there are open temp tables.
+SET SESSION binlog_format = STATEMENT;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+STATEMENT
+INSERT INTO t1 VALUES ('statement based');
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+STATEMENT
+# Test allow switching @@SESSION.binlog_format from STATEMENT to
+# MIXED when there are open temp tables.
+SET SESSION binlog_format = MIXED;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+MIXED
+# Test allow switching @@SESSION.binlog_format from MIXED to MIXED
+# when there are open temp tables.
+SET SESSION binlog_format = MIXED;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+MIXED
+INSERT INTO t2 VALUES (UUID());
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+MIXED
+# Test forbit switching @@SESSION.binlog_format from MIXED to STATEMENT 
+# when there are open temp tables and we are logging in row based format.
+SET SESSION binlog_format = STATEMENT;
+ERROR HY000: Cannot switch out of the row-based binary log format when the session has open temporary tables
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+MIXED
+SET SESSION binlog_format = ROW;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+ROW
+INSERT INTO t1 VALUES ('row based');
+# Test allow switching @@SESSION.binlog_format from ROW to MIXED 
+# when there are open temp tables.
+SET SESSION binlog_format = MIXED;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+MIXED
+INSERT INTO t1 VALUES ('row based');
+# Test allow switching @@SESSION.binlog_format from MIXED to ROW
+# when there are open temp tables.
+SET SESSION binlog_format = ROW;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+ROW
+# Test allow switching @@SESSION.binlog_format from ROW to ROW
+# when there are open temp tables.
+SET SESSION binlog_format = ROW;
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+ROW
+INSERT INTO t1 VALUES ('row based');
+# Test forbit switching @@SESSION.binlog_format from ROW to STATEMENT
+# when there are open temp tables.
+SET SESSION binlog_format = STATEMENT;
+ERROR HY000: Cannot switch out of the row-based binary log format when the session has open temporary tables
+SELECT @@SESSION.binlog_format;
+@@SESSION.binlog_format
+ROW
+DROP TEMPORARY TABLE t2;
+DROP TABLE t1;
diff --git a/mysql-test/suite/binlog/t/binlog_format_switch_in_tmp_table.test b/mysql-test/suite/binlog/t/binlog_format_switch_in_tmp_table.test
new file mode 100644
index 00000000000..6868506008c
--- /dev/null
+++ b/mysql-test/suite/binlog/t/binlog_format_switch_in_tmp_table.test
@@ -0,0 +1,76 @@
+#
+# Bug #45855 row events in binlog after switch from binlog_fmt=mix to stmt with open tmp tbl
+# Bug #45856 can't switch from binlog_format=row to mix with open tmp tbl
+# This test verfies if the program will generate ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR
+# error and forbid switching @@SESSION.binlog_format from MIXED or ROW to
+# STATEMENT when there are open temp tables and we are logging in row format.
+# There is no error in any other case.
+#
+
+source include/have_binlog_format_mixed.inc;
+
+SELECT @@SESSION.binlog_format;
+CREATE TABLE t1 (a VARCHAR(100));
+CREATE TEMPORARY TABLE t2 (a VARCHAR(100));
+
+--echo # Test allow switching @@SESSION.binlog_format from MIXED to STATEMENT
+--echo # when there are open temp tables and we are logging in statement based format.
+SET SESSION binlog_format = STATEMENT;
+SELECT @@SESSION.binlog_format;
+
+--echo # Test allow switching @@SESSION.binlog_format from STATEMENT to
+--echo # STATEMENT when there are open temp tables.
+SET SESSION binlog_format = STATEMENT;
+SELECT @@SESSION.binlog_format;
+
+INSERT INTO t1 VALUES ('statement based');
+SELECT @@SESSION.binlog_format;
+--echo # Test allow switching @@SESSION.binlog_format from STATEMENT to
+--echo # MIXED when there are open temp tables.
+SET SESSION binlog_format = MIXED;
+SELECT @@SESSION.binlog_format;
+
+--echo # Test allow switching @@SESSION.binlog_format from MIXED to MIXED
+--echo # when there are open temp tables.
+SET SESSION binlog_format = MIXED;
+SELECT @@SESSION.binlog_format;
+
+INSERT INTO t2 VALUES (UUID());
+SELECT @@SESSION.binlog_format;
+
+--echo # Test forbit switching @@SESSION.binlog_format from MIXED to STATEMENT 
+--echo # when there are open temp tables and we are logging in row based format.
+--ERROR ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR
+SET SESSION binlog_format = STATEMENT;
+SELECT @@SESSION.binlog_format;
+
+SET SESSION binlog_format = ROW;
+SELECT @@SESSION.binlog_format;
+
+INSERT INTO t1 VALUES ('row based');
+--echo # Test allow switching @@SESSION.binlog_format from ROW to MIXED 
+--echo # when there are open temp tables.
+SET SESSION binlog_format = MIXED;
+SELECT @@SESSION.binlog_format;
+
+INSERT INTO t1 VALUES ('row based');
+--echo # Test allow switching @@SESSION.binlog_format from MIXED to ROW
+--echo # when there are open temp tables.
+SET SESSION binlog_format = ROW;
+SELECT @@SESSION.binlog_format;
+
+--echo # Test allow switching @@SESSION.binlog_format from ROW to ROW
+--echo # when there are open temp tables.
+SET SESSION binlog_format = ROW;
+SELECT @@SESSION.binlog_format;
+
+INSERT INTO t1 VALUES ('row based');
+--echo # Test forbit switching @@SESSION.binlog_format from ROW to STATEMENT
+--echo # when there are open temp tables.
+--ERROR ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR
+SET SESSION binlog_format = STATEMENT;
+SELECT @@SESSION.binlog_format;
+
+DROP TEMPORARY TABLE t2;
+DROP TABLE t1;
+
diff --git a/sql/set_var.cc b/sql/set_var.cc
index d9bd14564bf..9dfbf2c7a6c 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -1294,6 +1294,25 @@ bool sys_var_thd_binlog_format::check(THD *thd, set_var *var) {
   bool result= sys_var_thd_enum::check(thd, var);
   if (!result)
     result= check_log_update(thd, var);
+  /*
+    If RBR and open temporary tables, their CREATE TABLE may not be in the
+    binlog, so we can't toggle to SBR in this connection.
+
+    If binlog_format=MIXED, there are open temporary tables, and an unsafe
+    statement is executed, then subsequent statements are logged in row
+    format and hence changes to temporary tables may be lost. So we forbid
+    switching @@SESSION.binlog_format from MIXED to STATEMENT when there are
+    open temp tables and we are logging in row format.
+  */
+  if (thd->temporary_tables && var->type == OPT_SESSION &&
+      var->save_result.ulong_value == BINLOG_FORMAT_STMT &&
+      ((thd->variables.binlog_format == BINLOG_FORMAT_MIXED &&
+        thd->is_current_stmt_binlog_format_row()) ||
+       thd->variables.binlog_format == BINLOG_FORMAT_ROW))
+  {
+    my_error(ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR, MYF(0));
+    return 1;
+  }
   return result;
 }
 
@@ -1303,23 +1322,6 @@ bool sys_var_thd_binlog_format::is_readonly() const
     Under certain circumstances, the variable is read-only (unchangeable):
   */
   THD *thd= current_thd;
-  /*
-    If RBR and open temporary tables, their CREATE TABLE may not be in the
-    binlog, so we can't toggle to SBR in this connection.
-    The test below will also prevent SET GLOBAL, well it was not easy to test
-    if global or not here.
-    And this test will also prevent switching from RBR to RBR (a no-op which
-    should not happen too often).
-
-    If we don't have row-based replication compiled in, the variable
-    is always read-only.
-  */
-  if ((thd->variables.binlog_format == BINLOG_FORMAT_ROW) &&
-      thd->temporary_tables)
-  {
-    my_error(ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR, MYF(0));
-    return 1;
-  }
   /*
     if in a stored function/trigger, it's too late to change mode
   */