postgis error with json-c

postgis.txt

% brew install postgis
==> Downloading http://download.osgeo.org/postgis/source/postgis-2.1.2.tar.gz
Already downloaded: /Library/Caches/Homebrew/postgis-2.1.2.tar.gz
==> ./autogen.sh
;==> ./configure --with-projdir=/usr/local --with-jsondir=/usr/local/opt/json-c --with-pgconfig=/usr/local/Cellar/postgresql/9.3.4/bin/pg_config --disable-nls
checking proj_api.h usability... yes
checking proj_api.h presence... yes
checking for proj_api.h... yes
checking for pj_get_release in -lproj... yes
configure: error: Cannot find json dev files in "/usr/local/opt/json-c"

READ THIS: https://github.com/Homebrew/homebrew/wiki/troubleshooting

These open issues may also help:
Postgis sql files not found (https://github.com/Homebrew/homebrew/issues/26604)

I get the same issue with formula posgis20:
brew install -vd postgis20
...
configure: error: Cannot find json dev files in "/usr/local/opt/json-c"
/usr/local/Library/Homebrew/debrew.rb:11:in `raise'
BuildError: Failed executing: ./configure --disable-dependency-tracking --with-projdir=/usr/local --with-jsondir=/usr/local/opt/json-c --with-pgconfig=/usr/local/Cellar/postgresql92/9.2.8_1/bin/pg_config --disable-nls

but json-c is installed properly:
xxxxxx@xxxxxx /usr/lib $ ls -all /usr/local/opt/json-c/lib/
total 352
drwxr-xr-x 6 xxxxxx admin 204B 13 Apr 16:55 ./
drwxr-xr-x 11 xxxxxx admin 374B 13 Apr 16:55 ../
-r--r--r-- 1 xxxxxx admin 76K 13 Apr 16:55 libjson-c.2.dylib
-r--r--r-- 1 xxxxxx admin 90K 13 Apr 16:55 libjson-c.a
lrwxr-xr-x 1 xxxxxx admin 17B 13 Apr 16:55 libjson-c.dylib@ -> libjson-c.2.dylib
drwxr-xr-x 3 xxxxxx admin 102B 13 Apr 16:55 pkgconfig/

Can someone help me?

@PixelDuck - Sorry about that. Will be fixed when https://github.com/Homebrew/homebrew-versions/pull/774 is merged.