[U-Boot] u-boot hangs waiting for serial input

I have compiled an older version of u-boot for ARM versatilepb board and booted in qemu as: qemu-system-arm -M versatilepb -m 128M -nographic -kernel flash.bin

It boots fine, basic commans like `printenv` works. However, issuing `loads` makes the bootloader wait indefinitely. No keypress works. The prompt comes back if the command aborted by pressing Ctrl+C. I am not sure if it is u-boot or qemu is misbehaving. Any suggestion?