When DOS receives commands, it checks to ensure the current BASIC interpreter is running in order to allow you to respond to an input statement with "Running", instead of trying to run the "Ning" file. The commands which cause these errors are listed on page 122 of the DOS manual.
The following relocatable machine language routine insures that DOS is satisfied.
LDA #$80
STA $33 This location must not equal $DD
STA $76 This location must not equal $FF
STA $D9 This location must be greater than $7F
RTS