diff --git a/bin/pt-online-schema-change b/bin/pt-online-schema-change
index f76e8723..c52e5bad 100755
--- a/bin/pt-online-schema-change
+++ b/bin/pt-online-schema-change
@@ -9777,6 +9777,9 @@ sub exec_nibble {
       # Ignore this warning because we have purposely set statement-based
       # replication.
       1592 => 1,
+      # Error: 1062 SQLSTATE: 23000 ( ER_DUP_ENTRY )
+      # Message: Duplicate entry '%ld' for key '%s'
+      # MariaDB 5.5.28+ has this as a warning; See https://bugs.launchpad.net/percona-toolkit/+bug/1099836
       1062 => 1,
    );
          
diff --git a/sandbox/start-sandbox b/sandbox/start-sandbox
index df668b1f..5b7e0179 100755
--- a/sandbox/start-sandbox
+++ b/sandbox/start-sandbox
@@ -27,6 +27,13 @@ debug_sandbox() {
    fi
 }
 
+mysql_upgrade_on() {
+   local cnf_file="$1"
+   local upgrade="$(which mysql_upgrade)"
+
+   $upgrade --defaults-file=$cnf_file --skip-write-binlog
+}
+
 make_sandbox() {
    # Make the sandbox dir and extract the base files.
    rm -rf /tmp/$port || die "Failed to rm /tmp/$port"
@@ -138,6 +145,10 @@ make_sandbox() {
    /tmp/$port/use -e "CREATE TABLE IF NOT EXISTS percona_test.sentinel (id INT PRIMARY KEY, ping VARCHAR(64) NOT NULL DEFAULT '')";
    /tmp/$port/use -e "REPLACE INTO percona_test.sentinel (id, ping) VALUES (1, '')";
 
+   if [ -n "${MYSQL_UPGRADE:-""}" ]; then
+      mysql_upgrade_on /tmp/$port/my.sandbox.cnf
+   fi
+
    # If the sandbox is a slave, start the slave.
    if [ "$type" = "slave" ]; then
       /tmp/$port/use -e "change master to master_host='127.0.0.1', master_user='msandbox', master_password='msandbox', master_port=$master_port"