fontcustom install error

$ fontcustom compile images/iconfont/
create fonts/fontcustom-test-icons/.fontcustom-data
ERROR: Compilation failed unexpectedly. Check your options and try again with --debug get more details.
$ fontcustom compile images/iconfont/ --debug
DEBUG: (raw output from fontforge)
["I'm sorry this file is too complex for me to understand (or is erroneous)", "I'm sorry this file is too complex for me to understand (or is erroneous)", "{\"glyphs\": [\"handlebars\", \"monocle\", \"mustache\", \"fontcustom_fb6c142df2e5fdeb110445d8a8a58d09\", \"fontcustom_b84592b302edcdc37a0eba43e9212360\", \"fontcustom_41353d4af21650645e3e76e50e6df392\"], \"fonts\": [\"fontcustom-test-icons.ttf\", \"fontcustom-test-icons.woff\", \"fontcustom-test-icons.eot\", \"fontcustom-test-icons.svg\"], \"file_name\": \"fontcustom-test-icons\"}"] ERROR: Compilation failed unexpectedly. Check your options and try again with --debug get more details.
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