2 files changed, 16 insertions, 6 deletions
diff --git a/activemodel/lib/active_model/validations/callbacks.rb b/activemodel/lib/active_model/validations/callbacks.rb
index a8fb4fdfc2..e28ad2841b 100644
--- a/activemodel/lib/active_model/validations/callbacks.rb
+++ b/activemodel/lib/active_model/validations/callbacks.rb
@@ -1,5 +1,3 @@
-require 'active_support/callbacks'
-
 module ActiveModel
   module Validations
     # == Active \Model Validation Callbacks
@@ -85,8 +83,8 @@ module ActiveModel
         #   person = Person.new
         #   person.name = ''
         #   person.valid? # => false
-        #   person.status # => false
-        #   person.name = 'bob'
+        #   person.status # => false
+        #   person.name = 'bob'
         #   person.valid? # => true
         #   person.status # => true
         def after_validation(*args, &block)
diff --git a/activemodel/lib/active_model/validations/length.rb b/activemodel/lib/active_model/validations/length.rb
index 70ef589cd7..675fb5f1e5 100644
--- a/activemodel/lib/active_model/validations/length.rb
+++ b/activemodel/lib/active_model/validations/length.rb
@@ -14,6 +14,10 @@ module ActiveModel
           options[:minimum], options[:maximum] = range.min, range.max
         end
 
+        if options[:allow_blank] == false && options[:minimum].nil? && options[:is].nil?
+          options[:minimum] = 1
+        end
+
         super
       end
 
@@ -40,7 +44,10 @@ module ActiveModel
 
         CHECKS.each do |key, validity_check|
           next unless check_value = options[key]
-          next if value_length.send(validity_check, check_value)
+
+          if !value.nil? || skip_nil_check?(key)
+            next if value_length.send(validity_check, check_value)
+          end
 
           errors_options[:count] = check_value
 
@@ -58,6 +65,10 @@ module ActiveModel
           options[:tokenizer].call(value)
         end || value
       end
+
+      def skip_nil_check?(key)
+        key == :maximum && options[:allow_nil].nil? && options[:allow_blank].nil?
+      end
     end
 
     module HelperMethods
@@ -79,7 +90,8 @@ module ActiveModel
       #
       # Configuration options:
       # * <tt>:minimum</tt> - The minimum size of the attribute.
-      # * <tt>:maximum</tt> - The maximum size of the attribute.
+      # * <tt>:maximum</tt> - The maximum size of the attribute. Allows +nil+ by
+      #   default if not used with :minimum.
       # * <tt>:is</tt> - The exact size of the attribute.
       # * <tt>:within</tt> - A range specifying the minimum and maximum size of
       #   the attribute.