External RAM as heap on lpc1788, large ZI

I'm using 8MiB external ram with the LPC1788. I use a scatter file to use it as heap.
I found out the startup file uses a lot of ZI-data. I think it tries to initialize the external ram. But the ram is setup by a function called by the main.
How do I prevent the startup file from initializing the external ram?

; *************************************************************
; *** Scatter-Loading Description File generated by uVision ***
; *************************************************************
; based on http://www.keil.com/forum/23045/setup-heap-on-external-ram/

LR_IROM1 0x00000000 0x00080000  {    ; load region size_region
  ER_IROM1 0x00000000 0x00080000  {  ; load address = execution address
   *.o (RESET, +First)
   *(InRoot$$Sections)
   .ANY (+RO)
  }
  RW_IRAM1 0x10000000 0x00010000  {  ; RW data
   .ANY (+RW +ZI)
  }
  RW_IRAM2 0x20000000 0x00008000  {
   .ANY (+RW +ZI)
  }
  RW_IRAM3 0xA0000000 0x00800000  { ; use malloc in external ram
   .ANY (HEAP) ; Object/Section directive, park HEAP in here
  }
}