Common Issue: April 2015 fixes for SharePoint 2013 might not install on Sharepoint 2013 SP1 slipstream builds (updated May 12th)
A couple of customers already ran into this issue: if you created your farm based on the SharePoint 2013 SP1 slipstream build available on MSDN and VLSC you might not be able to install the latest patches (April CU and PU). The reason is that starting in April the RTM baseline is no longer supported […]