CCS/TMS320F28377D: Heap (malloc) in External Memory

Tool/software: Code Composer Studio

My hardware is using an F28377D connected to an external SDRAM.  Everything is working fine with the SDRAM.  I can copy and work with large amounts of data on it.

The code also dynamically allocates memory on the heap for certain tasks.  This works OK when the heap is defined in the linker in internal memory:

RAMGS5 : origin = 0x011000, length = 0x001000

.esysmem : > RAMGS5 PAGE = 1

The problem now is that I need to allocate much larger amounts of memory than 0x1000 words.  I don't have any more resources in internal RAM so I need to use my external SDRAM to store the heap.  I changed my linker file to include these lines:

EMIF1_CS0nA : origin = 0x80000000, length = 0x200000 // An 8Mbyte SDRAM chip connected to EMIF1 CS0 (low 4 MBytes)
EMIF1_CS0nB : origin = 0x80200000, length = 0x200000 // An 8Mbyte SDRAM chip connected to EMIF1 CS0 (high 4 Mbytes)

.esysmem : > EMIF1_CS0nB PAGE = 1 //used for mallocs

Even if I leave my heap size at 0x1000 in the linker settings, every time I call malloc now, it returns NULL.  Note that I am NOT using any RTOS.  

Is there some other Linker setting I am missing?