Nios app having 'malloc' ref throws error when it is run on Nios ISS Configuration

I have written small c program and trying to run on the Nios ISS simulator.

I am facing strange problem in running application if I make a reference to 'malloc' to allocate memory. Actually, the code compiles and links but when it is running throws following error, shown below -

Error! : Failed memory access in component cpu - Reading data 0x0 from uninitial

ized memory (addr = 0x4022bfc)

Error! : Simulation failed in component cpu at instruction 1312943 (PC=0x4016750

instr=0x10800017).

If I remove malloc reference, code runs properly without an error.

What could be the problem? is it a limitation of Simulator?

Regards,

Sanjeev