Cowboy webserver crashes on startup after adding ibrowse dependency to Makefile - makefile

Question

I'm currently developing a server in Erlang using Cowboy as the web server framework. At startup, I need to be able to make server-side HTTP calls to fetch files from other web servers, so I've included a Makefile dependency to ibrowse
The ibrowse documentation does not mention anything specifically about being added as a Cowboy dependency, but the erlang.mk documentation indicates that I only need to add the single line
DEPS = ibrowse
However, as soon as I add this line, Cowboy crashes on startup with
=INFO REPORT==== 15-Feb-2018::14:51:13 ===
application: geo_server
exited: {bad_return,
{{geo_server_app,start,[normal,[]]},
{'EXIT',
{undef,
[{cowboy_router,compile,
[[{'_',
[{"/",default_handler,[]},
{"/client_info",client_info_handler,[]},
{"/search",request_handler,[]}]}]],
[]},
{geo_server_app,start,2,
[{file,"src/geo_server_app.erl"},{line,8}]},
{application_master,start_it_old,4,
[{file,"application_master.erl"},
{line,273}]}]}}}}
type: permanent
{"Kernel pid terminated",application_controller,"{application_start_failure,geo_server,{bad_return,{{geo_server_app,start,[normal,[]]},{'EXIT',{undef,[{cowboy_router,compile,[[{'_',[{\"/\",default_handler,[]},{\"/client_info\",client_info_handler,[]},{\"/search\",request_handler,[]}]}]],[]},{geo_server_app,start,2,[{file,\"src/geo_server_app.erl\"},{line,8}]},{application_master,start_it_old,4,[{file,\"application_master.erl\"},{line,273}]}]}}}}}"}
Kernel pid terminated (application_controller) ({application_start_failure,geo_server,{bad_return,{{geo_server_app,start,[normal,[]]},{'EXIT',{undef,[{cowboy_router,compile,[[{'_',[{"/",default_handle
heart: Thu Feb 15 14:51:14 2018: Erlang is crashing .. (waiting for crash dump file)
heart: Thu Feb 15 14:51:14 2018: Would reboot. Terminating.
gmake: *** [erlang.mk:6639: run] Error 1
Take this dependency away, and Cowboy starts up fine.
PROJECT = geo_server
PROJECT_DESCRIPTION = Geographic information server
PROJECT_VERSION = 0.1.0
DEPS = cowboy
dep_cowboy_commit = 2.2.2
DEP_PLUGINS = cowboy
include erlang.mk
DEPS = ibrowse
It also doesn't matter whether I put the DEPS = ibrowse before or after the line include elrang.mk.
After some more noodling around, this seems to a caching problem in the way Cowboy's make run process works.
Adding ibrowse seems to require two calls to make run. If my code then crashes, I have to add and then remove ibrowse again before I can see my amended code running.
Thanks
Chris W

Answer 1

From erlang.mk documentation
DEPS List of applications this project depends on that need to be
fetched by Erlang.mk.
Solution:
DEPS = cowboy ibrowse

Answer 2

The DEPS need only occur once and contains a space separated list of dependencies