diff --git a/mysql-test/suite/binlog/r/binlog_mysqlbinlog_row_frag.result b/mysql-test/suite/binlog/r/binlog_mysqlbinlog_row_frag.result
index 041be5ed09f..3ae5519fe00 100644
--- a/mysql-test/suite/binlog/r/binlog_mysqlbinlog_row_frag.result
+++ b/mysql-test/suite/binlog/r/binlog_mysqlbinlog_row_frag.result
@@ -20,5 +20,8 @@ ERROR 42000: You have an error in your SQL syntax; check the manual that corresp
 SET @binlog_fragment_0='012345';
 BINLOG @binlog_fragment_0, @binlog_fragment_not_exist;
 ERROR 42000: Incorrect argument type to variable 'binlog_fragment_not_exist'
+SET @a= '42';
+BINLOG @a, @a;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use
 # Cleanup
 DROP TABLE t;
diff --git a/mysql-test/suite/binlog/t/binlog_mysqlbinlog_row_frag.test b/mysql-test/suite/binlog/t/binlog_mysqlbinlog_row_frag.test
index f0317ef1219..40360421c6b 100644
--- a/mysql-test/suite/binlog/t/binlog_mysqlbinlog_row_frag.test
+++ b/mysql-test/suite/binlog/t/binlog_mysqlbinlog_row_frag.test
@@ -40,6 +40,11 @@ SET @binlog_fragment_0='012345';
 --error ER_WRONG_TYPE_FOR_VAR
 BINLOG @binlog_fragment_0, @binlog_fragment_not_exist;
 
+# MDEV-22520
+SET @a= '42';
+--error ER_SYNTAX_ERROR
+BINLOG @a, @a;
+
 --echo # Cleanup
 --remove_file $MYSQLTEST_VARDIR/tmp/mysqlbinlog.sql
 DROP TABLE t;
diff --git a/sql/sql_binlog.cc b/sql/sql_binlog.cc
index 1105c9a55ec..b8d4525b5d7 100644
--- a/sql/sql_binlog.cc
+++ b/sql/sql_binlog.cc
@@ -78,8 +78,9 @@ int binlog_defragment(THD *thd)
     memcpy(thd->lex->comment.str + gathered_length, entry[k]->value,
            entry[k]->length);
     gathered_length += entry[k]->length;
-    update_hash(entry[k], true, NULL, 0, STRING_RESULT, &my_charset_bin, 0);
   }
+  for (uint k=0; k < 2; k++)
+    update_hash(entry[k], true, NULL, 0, STRING_RESULT, &my_charset_bin, 0);
 
   DBUG_ASSERT(gathered_length == thd->lex->comment.length);