"Check failed: size_in_datum == data_size" error while creating mean image, how to solve?

Question

I am trying to generate the mean image from training data in caffe. My data is 256x256 grayscale images. I created lmdb by using create_imagenet.sh by replacing --shuffle with --gray.

I edited create_imagenet.sh as follows:

GLOG_logtostderr=1 $TOOLS/convert_imageset \
    --resize_height=$RESIZE_HEIGHT \
    --resize_width=$RESIZE_WIDTH \
    --gray \
    $TRAIN_DATA_ROOT \
    $DATA/train.txt \
    $EXAMPLE/train_lmdb

echo "Creating val lmdb..."

GLOG_logtostderr=1 $TOOLS/convert_imageset \
    --resize_height=$RESIZE_HEIGHT \
    --resize_width=$RESIZE_WIDTH \
    --gray \
    $VAL_DATA_ROOT \
    $DATA/val.txt \
    $EXAMPLE/val_lmdb

echo "Done."

I successfully generated my LMDB databases. But I am still getting the following error while creating mean image.

 F0105 14:50:52.470038  2191 compute_image_mean.cpp:77] Check failed: size_in_datum == data_size (64000 vs. 65536) Incorrect data field size 64000
*** Check failure stack trace: ***
    @     0x7faa4978d5cd  google::LogMessage::Fail()
    @     0x7faa4978f433  google::LogMessage::SendToLog()
    @     0x7faa4978d15b  google::LogMessage::Flush()
    @     0x7faa4978fe1e  google::LogMessageFatal::~LogMessageFatal()
    @           0x402be1  main
    @     0x7faa486da830  __libc_start_main
    @           0x403249  _start
    @              (nil)  (unknown)
Aborted (core dumped)

I am sure all images have the same size and format. Does anyone have any suggestion to tackle this error?

Your help is really appreciated.