CoreText: Invalid 'kern' Subtable In name ios 7

Question

As of iOS 7 I now see my console filled with the following:

CoreText: Invalid 'kern' Subtable In name = Volkswagen-Bold, size =
17.000000, matrix = 0x0, descriptor = <CTFontDescriptor: 0x10a79370>{attributes = <CFBasicHash 0x10a793a0 [0x537fec8]>{type = mutable dict, count = 1,

entries =>

     1 : <CFString 0x6a9df90 [0x537fec8]>{contents = "NSFontNameAttribute"} = <CFString 0x10a795e0 [0x537fec8]>{contents = "Volkswagen-Bold"}

}

>}

When I install the font and validate it in FontBook the kern checks out fine. iOS 6 has no issues with this font, I am not exactly sure what to do to fix this. I ran ftxdumperfuser on the font and this is the output, looks normal...Any ideas?

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<!DOCTYPE hheaTable [
<!ELEMENT hheaTable EMPTY>
<!ATTLIST hheaTable versionMajor CDATA #IMPLIED
     versionMinor CDATA #IMPLIED
     ascender CDATA #IMPLIED
     descender CDATA #IMPLIED
     lineGap CDATA #IMPLIED
     advanceWidthMax CDATA #IMPLIED
     minLeftSideBearing CDATA #IMPLIED
     minRightSideBearing CDATA #IMPLIED
     xMaxExtent CDATA #IMPLIED
     caretSlopeRise CDATA #IMPLIED
     caretSlopeRun CDATA #IMPLIED
     caretOffset CDATA #IMPLIED
     metricDataFormat CDATA #IMPLIED
     numberOfHMetrics CDATA #IMPLIED
>
]>

<!--

     Data generated      Tue Nov  5 11:48:57 2013

     Generated by ftxdumperfuser build 248,
          FontToolbox.framework build 55

     Font full name: 'Volkswagen-Bold'

-->

<hheaTable
     versionMajor="1"
     versionMinor="0"
     ascender="978"
     descender="-239"
     lineGap="0"
     advanceWidthMax="1042"
     minLeftSideBearing="-90"
     minRightSideBearing="-82"
     xMaxExtent="1009"
     caretSlopeRise="1"
     caretSlopeRun="0"
     caretOffset="0"
     metricDataFormat="0"
     numberOfHMetrics="231"
     />

Answer 1

The font was originally a ttf, and I finally found a version that was an otf and that resolved the issue. I don't think it has anything to do with the file extension, but rather how the data was created or saved.