Fedora 21
grep (GNU grep) 2.21

Grep detects text file as Binary. File is attached.

file Makefile 
Makefile: ISO-8859 text

ack PKG_NAME
Makefile
10:PKG_NAME:=clearsilver
14:PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz

grep --version ; grep "PKG_NAME" Makefile
grep (GNU grep) 2.7
...
PKG_NAME:=clearsilver
PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz

grep --version ; grep "PKG_NAME" Makefile
grep (GNU grep) 2.21
...
Binary file Makefile matches