diff --git a/src/gmconfig.erl b/src/gmconfig.erl
index 411b3d7..25410b1 100644
--- a/src/gmconfig.erl
+++ b/src/gmconfig.erl
@@ -60,8 +60,9 @@
 -include_lib("kernel/include/logger.hrl").
 
 -type gmconfig() :: #{ os_env_prefix => string()
-                     , config_file_basename => string
-                     , config_file_search_path => [string()]
+                     , config_file_basename => string() | 'undefined'
+                     , config_file_os_env => string() | 'undefined'
+                     , config_file_search_path => [string() | fun(() -> string())]
                      , system_suffix => string()
                      , schema => string() | map() | fun(() -> map())}.
 
@@ -124,10 +125,30 @@ gmconfig_env(Key) ->
 gmconfig_env(Key, Default) ->
     maps:get(Key, gmconfig_env(), Default).
 
+search_path() -> search_path(config_file).
+
+search_path(Kind) ->
+    Key = case Kind of
+              config_file -> config_file_search_path;
+              system_defaults -> system_defaults_search_path
+          end,
+    case gmconfig_env(Key, undefined) of
+        undefined -> [];
+        Path0 when is_list(Path0) ->
+            lists:map(
+              fun(F) when is_function(F, 0) ->
+                      F();
+                 (D) when is_list(D) ->
+                      D
+              end, Path0)
+    end.
+
 default_gmconfig() ->
     #{ os_env_prefix => "GM"
      , config_file_basename => "gmconfig"
+     , config_file_os_env => undefined
      , config_file_search_path => ["."]
+     , system_defaults_search_path => [fun setup:data_dir/0]
      , system_suffix => "" }.
 
 %% This function is similar to application:get_env/2, except
@@ -606,22 +627,25 @@ command_line_config_file() ->
     end.
 
 default_config_file() ->
-    case os:getenv("GAJUMARU_CONFIG") of
-        false ->
-            case setup:get_env(aecore, config) of
-                {ok, F} -> F;
-                _       -> search_default_config()
-            end;
-        F ->
-            F
+    case gmconfig_env(config_file_os_env, undefined) of
+        undefined ->
+            search_default_config();
+        E ->
+            case os:getenv(E) of
+                false -> search_default_config();
+                F     -> F
+            end
     end.
 
 search_default_config() ->
-    Dirs = [filename:join([os:getenv("HOME"), ".gajumaru", "gajumaru"]),
-            setup:home()],
-    SystemSuffix = get_system_suffix(),
-    Fname = "gajumaru" ++ SystemSuffix ++ ".{json,yaml}",
-    search_for_config_file(Dirs, Fname).
+    case gmconfig_env(config_file_basename, undefined) of
+        undefined -> undefined;
+        Basename ->
+            Dirs = search_path(),
+            SystemSuffix = get_system_suffix(),
+            Fname = Basename ++ SystemSuffix ++ ".{json,yaml}",
+            search_for_config_file(Dirs, Fname)
+    end.
 
 search_for_config_file(Dirs, FileWildcard) ->
     lists:foldl(
@@ -1006,14 +1030,20 @@ load_system_defaults() ->
     load_system_defaults(report).
 
 load_system_defaults(Mode) ->
-    SystemSuffix = get_system_suffix(),
-    Fname = "gajumaru_defaults" ++ SystemSuffix ++ ".{yaml,json}",
-    case search_for_config_file([setup:data_dir()], Fname) of
+    case gmconfig_env(config_file_basename, undefined) of
         undefined ->
             ok;
-        ConfigFile ->
-            ?LOG_DEBUG("Loading system defaults from ~s", [ConfigFile]),
-            load_config_file(ConfigFile, Mode)
+        Basename ->
+            SystemSuffix = get_system_suffix(),
+            Fname = Basename ++ "_defaults" ++ SystemSuffix ++ ".{yaml,json}",
+            Path = search_path(system_defaults),
+            case search_for_config_file(Path, Fname) of
+                undefined ->
+                    ok;
+                ConfigFile ->
+                    ?LOG_DEBUG("Loading system defaults from ~s", [ConfigFile]),
+                    load_config_file(ConfigFile, Mode)
+            end
     end.
 
 get_system_suffix() ->