Changes to userPassword attribute not reflected by server immediately, if performed by another user

Changes to userPassword attribute seem not to be reflected by server immediately, if performed by another user. Here is what I did:

(1) Add this entry to the directory:

—
dn: cn=Tori Amos,dc=example,dc=com
sn: Amos
objectClass: person
objectClass: top
cn: Tori Amos
userpassword: secret
—

$ ldapmodify -h localhost -p 10389 -D "uid=admin,ou=system" -w secret -a -f tori.ldif
adding new entry cn=Tori Amos,dc=example,dc=com

(2) Check, that Tori can authenticate

$ ldapsearch -h localhost -p 10389 -D "cn=Tori Amos,dc=example,dc=com" -w secret -b "" -s base "(objectClass=*)" vendorName
version: 1
dn:
vendorName: Apache Software Foundation

(3) Modify Tori's password

LDIF-File:

—
dn: cn=Tori Amos,dc=example,dc=com
changetype: modify
replace: userPassword
userPassword: geheim
-
—

$ ldapmodify -h localhost -p 10389 -D "uid=admin,ou=system" -w secret -f changePwd.ldif
modifying entry cn=Tori Amos,dc=example,dc=com

Note, that I use the admin account to perform this operation!

(4) Check, whether it works

$ ldapsearch -h localhost -p 10389 -D "cn=Tori Amos,dc=example,dc=com" -w geheim -b "" -s base "(objectClass=*)" vendorName
ldap_simple_bind: Invalid credentials
ldap_simple_bind: additional info: Bind failed: null

$ ldapsearch -h localhost -p 10389 -D "cn=Tori Amos,dc=example,dc=com" -w secret -b "" -s base "(objectClass=*)" vendorName
version: 1
dn:
vendorName: Apache Software Foundation

I think this behavior is not correct, because the new password "geheim" should work immediately (as you assume as well). Note that the problem does not occur, if the user "Tori Amos" changes her password herself. In this case, the new password is valid immediately.