diff --git a/.circleci/config.yml b/.circleci/config.yml
index 20f09b6..c0ec14e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -54,6 +54,10 @@ erlang-docker-template: &erlang-docker-template
         name: run tests
         command: make circle-tests
         working_directory: ~/ldclient
+    - run:
+        name: Build documentation
+        command: make doc
+        working_directory: ~/ldclient
     - run:
         name: run dialyzer
         command: make dialyze
diff --git a/src/ldclient_config.erl b/src/ldclient_config.erl
index f76baae..8b29830 100644
--- a/src/ldclient_config.erl
+++ b/src/ldclient_config.erl
@@ -339,7 +339,7 @@ parse_application_info(ApplicationInfoMap) ->
         set_valid_tag(id, Id, undefined)).
 
 -spec set_valid_tag(Key :: atom(), Value :: binary() | undefined, MapOrUndefined :: map() | undefined) -> app_info() | undefined.
-set_valid_tag(Key, _Value = undefined, MapOrUndefined) -> MapOrUndefined;
+set_valid_tag(_Key, _Value = undefined, MapOrUndefined) -> MapOrUndefined;
 set_valid_tag(Key, Value, MapOrUndefined) ->
     case validate_tag_value(Value) of
         true ->
diff --git a/src/ldclient_headers.erl b/src/ldclient_headers.erl
index c85b8b5..142f17f 100644
--- a/src/ldclient_headers.erl
+++ b/src/ldclient_headers.erl
@@ -72,7 +72,7 @@ get_tags(Tag) ->
 %% @doc Combine all the tags into the format for application tags.
 %%
 %% Formatted tags are of the format `tag/value' a tag can have multiple values
-%% in that case it will be represented by space delimited pairs `tagA/valueA tagA/ValueB`.
+%% in that case it will be represented by space delimited pairs `tagA/valueA tagA/ValueB'.
 %% @end
 -spec combine_tags(Tags :: [{binary(), [binary()]}]) -> binary().
 combine_tags(Tags) -> combine_tags(Tags, <<>>).
@@ -117,6 +117,7 @@ add_version_tag(_Info, InList) -> InList.
 %%     {<<"b">>, [<<"1">>, <<"2">>, <<"3">>]},
 %%     {<<"c">>, [<<"1">>, <<"4">>, <<"5">>]}
 %% ]
+%% '''
 %% @end
 -spec sort_tags(Tags :: [{binary(), [binary()]}]) -> SortedTags :: [{binary(), [binary()]}].
 sort_tags(Tags) ->
diff --git a/src/ldclient_update_requestor_httpc.erl b/src/ldclient_update_requestor_httpc.erl
index 20df3af..ae00351 100644
--- a/src/ldclient_update_requestor_httpc.erl
+++ b/src/ldclient_update_requestor_httpc.erl
@@ -23,7 +23,7 @@
 %%===================================================================
 
 -spec init(Tag :: atom(), SdkKey :: string()) -> state().
-init(Tag, SdkKey) ->
+init(Tag, _SdkKey) ->
     Options = ldclient_config:get_value(Tag, http_options),
     HttpOptions = ldclient_http_options:httpc_parse_http_options(Options),
     DefaultHeaders = ldclient_headers:get_default_headers(Tag, string_pairs),