ifeq issue: compare 2 strings with a dot included

ifeq issue: compare 2 strings with a dot included

I am trying to implement a simple string comparison to get the type of a
file (using its extension) like this:
extract_pkg: $(PKG)
ifeq ($(EXT), .zip)
@echo "is zip file"
else
@echo "is not a zip file"
endif
extract_pkg : PKG = mypkg.zip
However, when I run it it goes into the else branch. My guess is, it has
to do with the dot, but I dont find a solution. Thanks for your help !