diff --git a/config/locales/en.yml b/config/locales/en.yml
index 4228b5b66..86a80eea3 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -29,3 +29,10 @@ en:
     api_documentation: API documentation
     headers: Headers
     header_name: Header name
+    must_be: "Must be %{string}"
+    must_be_one_of: "Must be one of: %{string}."
+    must_be_an_array_of: "Must be one of: %{string}."
+    must_be_a_number: Must be a number
+    must_be_a_hash: Must be a Hash
+    must_be_true_or_false: Must be 'true' or 'false' or '1' or '0'
+    must_be_an_array_of_nested_elements: Must be an Array of nested elements
diff --git a/lib/apipie/validator.rb b/lib/apipie/validator.rb
index e4bfa0e65..d4198b5b2 100644
--- a/lib/apipie/validator.rb
+++ b/lib/apipie/validator.rb
@@ -96,7 +96,7 @@ def self.build(param_description, argument, options, block)
       end
 
       def description
-        "Must be #{@type}"
+        I18n.t 'apipie.must_be', :string => @type, default: 'Must be %{string}'
       end
 
       def expected_type
@@ -150,7 +150,7 @@ def self.build(param_description, argument, options, proc)
 
       def description
         string = @array.map { |value| "<code>#{value}</code>" }.join(', ')
-        "Must be one of: #{string}."
+        I18n.t 'apipie.must_be_one_of', :string => string, default: 'Must be one of: %{string}.'
       end
     end
 
@@ -173,7 +173,7 @@ def process_value(values)
       end
 
       def description
-        "Must be an array of #{items}"
+        I18n.t 'apipie.must_be_an_array_of', :string => items, default: 'Must be an array of %{string}'
       end
 
       def expected_type
@@ -243,7 +243,7 @@ def self.build(param_description, argument, options, block)
       end
 
       def description
-        "Must be one of: #{@array.join(', ')}."
+        I18n.t 'apipie.must_be_one_of', :string => @array.join(', '), default: 'Must be one of: %{string}.'
       end
     end
 
@@ -327,7 +327,7 @@ def process_value(value)
       end
 
       def description
-        "Must be a Hash"
+        I18n.t 'apipie.must_be_a_hash', default: 'Must be a Hash'
       end
 
       def expected_type
@@ -388,7 +388,7 @@ def self.build(param_description, argument, options, block)
       end
 
       def description
-        "Must be a number."
+        I18n.t 'apipie.must_be_a_number', default: 'Must be a number'
       end
 
       def self.validate(value)
@@ -413,7 +413,7 @@ def expected_type
       end
 
       def description
-        "Must be 'true' or 'false' or '1' or '0'"
+        I18n.t 'apipie.must_be_true_or_false', default: "Must be 'true' or 'false' or '1' or '0'"
       end
     end
 
@@ -454,7 +454,7 @@ def expected_type
       end
 
       def description
-        "Must be an Array of nested elements"
+        I18n.t 'apipie.must_be_an_array_of_nested_elements', default: 'Must be an Array of nested elements'
       end
 
       def params_ordered