Problem when using Dockerfile COPY command

Hi,

I encountered an error when I try to run COPY --from=builder ${PROJECTS} wildfly/standalone/deployments/, the error message is COPY failed: no source files were specified

The environment variable PROJECTS includes project paths space separated.
when I do RUN echo ${PROJECTS} it gives me project_A_path project_B_path

The weird thing is if there is only one project, the COPY will success, but things went wrong when it goes to multiple projects. Another try is if I directly put the same multiple projects string in COPY instead the ${PROJECTS}, it works as well.

Any ideas?
Thanks!