if_auth.o, undefined reference to ieee80211 functions

I'm having trouble getting a kernel with the Atheros driver to compile.  I
get the following error during linking:

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linking kernel
if_ath.o: In function `ath_attach':
if_ath.o(.text+0x3ba): undefined reference to `ieee80211_media_status'
if_ath.o(.text+0x3ca): undefined reference to `ieee80211_media_init'
if_ath.o: In function `ath_chan2flags':
if_ath.o(.text+0x884): undefined reference to `ieee80211_chan2mode'
if_ath.o: In function `ath_init':
if_ath.o(.text+0x9e8): undefined reference to `ieee80211_chan2mode'
if_ath.o: In function `ath_media_change':
if_ath.o(.text+0x1260): undefined reference to `ieee80211_media_change'
if_ath.o: In function `ath_watchdog':
if_ath.o(.text+0x1352): undefined reference to `ieee80211_iterate_nodes'
if_ath.o: In function `ath_beacon_alloc':
if_ath.o(.text+0x1914): undefined reference to `ieee80211_add_rates'
if_ath.o(.text+0x1952): undefined reference to `ieee80211_add_xrates'
if_ath.o: In function `ath_chan_set':
if_ath.o(.text+0x383b): undefined reference to `ieee80211_chan2ieee'
if_ath.o(.text+0x384f): undefined reference to `ieee80211_chan2ieee'
if_ath.o(.text+0x3903): undefined reference to `ieee80211_chan2ieee'
if_ath.o(.text+0x3971): undefined reference to `ieee80211_chan2mode'
if_ath.o: In function `ath_newstate':
if_ath.o(.text+0x3d0b): undefined reference to `ieee80211_chan2ieee'
*** Error code 1

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My configuration file includes both 'device ath_hal' and 'device ath'.
Are there any other options that I am missing?