Addition to egreg's answer:
\label is redefined by package
nameref that is loaded by
\AtBeginDocument. Therefore it is enough to load
nameref before redefining:
But the redefinition can additionally be put into
\AtBeginDocument for the case there are other packages involved.
Also the questions talks about two labels, then additional stuff has to be done.
\label tries to be invisible regarding spaces. If space is detected before it suppresses the following spaces. This mechanism does not work for consecutive
\labels and the new definition should be surrounded by
What is the purpose of the added
vol1:? If the labels are used inside another document,
then packages that are able to import foreign labels (
zref-xr) usually allow the addition of a prefix for the label names. Assuming the main TeX file is called
firstvolume.tex, then the other document uses something like: