I have an Org-mode file with the block

  #+BEGIN_SRC prolog :goal main
    main :-
        write('Hello, world!').
  #+END_SRC

Running org-ctrl-c-ctrl-c on that block logs the message "org-babel-variable-assignments:prolog: Symbol’s function definition is void: org-babel--get-vars".

The result of evaluating (version) is "GNU Emacs 25.3.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.22.28) of 2018-03-07".
The result of evaluating (org-version) is "8.2.10".