SSIS Double-hop... how to solve?

I have what I assume to be a pretty standard setup: 1. ServerA running a web application as ServiceAccount1 2. ServerB running SSIS as ServiceAccount2. 3. ServerC hosting a network share that ServiceAccount1 has permissions to read from The web application initiates an SSIS package execution via SQL commands. The package tries to read a file from the network share and fails due to the double-hop problem (login failed on ServerC, "anonymous login". How can I get this to work? The SPNs are already there, and I've tried granting the delegation permission but SSIS refuses to forward on the credentials.