Just to add to Python's excellent message, Junos also has support for VSTP for interoperability with Cisco (or others) PVST+. If Cisco is running R-PVST+, then the Juniper side recommendation is to enable both RSTP and VSTP for proper interoperability.
It should be noted that in most proper network designs done in last 10+ years, the ability to remove any form of STP from a network is the best recommendation, IMHO. Based upon various newer (and some quite old!) technologies, network designs in 2017 should really never need any form of STP, outside of potential for interoperability with some very old products.