diff --git a/spec/ameba/config_spec.cr b/spec/ameba/config_spec.cr
index 6287de05..7b08f64c 100644
--- a/spec/ameba/config_spec.cr
+++ b/spec/ameba/config_spec.cr
@@ -85,7 +85,7 @@ module Ameba
       end
 
       it "raises when custom config file doesn't exist" do
-        expect_raises(Exception, "Config file is invalid: Unable to find config file foo.yml") do
+        expect_raises(Exception, "Config file is invalid: Config file does not exist foo.yml") do
           Config.load "foo.yml"
         end
       end
diff --git a/src/ameba/config.cr b/src/ameba/config.cr
index ad4f5dc6..2e5019de 100644
--- a/src/ameba/config.cr
+++ b/src/ameba/config.cr
@@ -120,7 +120,8 @@ class Ameba::Config
 
   protected def self.read_config(path = nil)
     if path
-      return File.exists?(path) ? File.read(path) : raise("Unable to find config file #{path}")
+      raise ArgumentError.new("Config file does not exist #{path}") unless File.exists?(path)
+      return File.read(path)
     end
     each_config_path do |config_path|
       return File.read(config_path) if File.exists?(config_path)