UffParser: Unsupported number of graph 0

Hi all, I am running the test trtexec with TRT5.1.2 and I got this error:
[I] uff: /workspace/tensorrt/python/data/resnet50/resnet50-infer-5.uff
[I] output: GPU_0/tower_0/Softmax
[I] uffInput: input,3,224,224
[I] iterations: 40
[I] int8
[I] batch: 1
[I] device: 0
[I] avgRuns: 100
[E] [TRT] UffParser: Unsupported number of graph 0
[E] Engine could not be created
[E] Engine could not be created
&&&& FAILED TensorRT.trtexec #