diff --git a/lib/sequel_enum.rb b/lib/sequel_enum.rb
index d19c438..7f7ddbb 100644
--- a/lib/sequel_enum.rb
+++ b/lib/sequel_enum.rb
@@ -12,14 +12,18 @@ def enums
 
         def enum(column, values)
           if values.is_a? Hash
-            values.each do |key,val|
+            values.each do |key, val|
               raise ArgumentError, "index should be a symbol, #{key} provided which it's a #{key.class}" unless key.is_a? Symbol
-              raise ArgumentError, "value should be an integer, #{val} provided which it's a #{val.class}" unless val.is_a? Integer
+
+              if !val.is_a?(Integer) || !val.is_a?(String)
+                raise ArgumentError, "value should be an integer or string, #{val} provided which it's a #{val.class}"
+              end
             end
+
           elsif values.is_a? Array
             values = Hash[values.map.with_index { |v, i| [v, i] }]
           else
-            raise ArgumentError, "#enum expects the second argument to be an array of symbols or a hash like { :symbol => integer }"
+            raise ArgumentError, "#enum expects the second argument to be an array of symbols or a hash like { :symbol => integer|string }"
           end
 
           define_method "#{column}=" do |value|
@@ -30,7 +34,7 @@ def enum(column, values)
             self.class.enums[column].rassoc(self[column])&.first
           end
 
-          values.each do |key, value|
+          values.each do |key, _|
             define_method "#{key}?" do
               self.send(column) == key
             end