diff --git a/lib/dry/inflector.rb b/lib/dry/inflector.rb
index b09d23a..cf01f25 100644
--- a/lib/dry/inflector.rb
+++ b/lib/dry/inflector.rb
@@ -8,6 +8,8 @@ class Inflector
     require "dry/inflector/version"
     require "dry/inflector/inflections"
 
+    attr_reader :inflections
+
     # Instantiate the inflector
     #
     # @param blk [Proc] an optional block to specify custom inflection rules
@@ -310,6 +312,17 @@ def to_s
     end
     alias_method :inspect, :to_s
 
+    # Freeze the inflector instance
+    #
+    # Forbid later additions to the inflector rules
+    #
+    # @since 1.1.0
+    #
+    def freeze
+      inflections.freeze
+      super
+    end
+
     private
 
     # @since 0.1.0
@@ -320,8 +333,6 @@ def to_s
     # @api private
     DEFAULT_SEPARATOR = " "
 
-    attr_reader :inflections
-
     # @since 0.1.3
     # @api private
     def internal_camelize(input, upper)
diff --git a/lib/dry/inflector/inflections.rb b/lib/dry/inflector/inflections.rb
index 2113746..6094161 100644
--- a/lib/dry/inflector/inflections.rb
+++ b/lib/dry/inflector/inflections.rb
@@ -149,6 +149,8 @@ def singular(rule, replacement)
       #     inflections.singular "octopus", "octopi"
       #   end
       def irregular(singular, plural)
+        raise FrozenError, "can't modify a frozen inflection" if frozen?
+
         uncountables.delete(singular)
         uncountables.delete(plural)
 
@@ -173,6 +175,8 @@ def irregular(singular, plural)
       #     inflections.uncountable %w(money information rice)
       #   end
       def uncountable(*words)
+        raise FrozenError, "can't modify a frozen inflection" if frozen?
+
         uncountables.merge(words.flatten)
       end
 
@@ -195,6 +199,8 @@ def uncountable(*words)
       #   inflector.camelize("html")        # => "HTML"
       #   inflector.underscore("HTMLIsFun") # => "html_is_fun"
       def acronym(*words)
+        raise FrozenError, "can't modify a frozen inflection" if frozen?
+
         words.each { |word| @acronyms.add(word.downcase, word) }
       end
 
@@ -222,9 +228,24 @@ def acronym(*words)
       #     inflections.human("legacy_col_person_name", "Name")
       #   end
       def human(rule, replacement)
+        raise FrozenError, "can't modify a frozen inflection" if frozen?
+
         humans.insert(0, [rule, replacement])
       end
 
+      # Freeze inflections
+      #
+      # @since 1.1.0
+      #
+      def freeze
+        @plurals.freeze
+        @singulars.freeze
+        @humans.freeze
+        @uncountables.freeze
+        @acronyms.freeze
+        super
+      end
+
       private
 
       # Add irregular inflection
@@ -250,6 +271,8 @@ def add_irregular(rule, replacement, target)
       # @since 0.1.0
       # @api private
       def rule(rule, replacement, target)
+        raise FrozenError, "can't modify a frozen inflection" if frozen?
+
         uncountables.delete(rule)
         uncountables.delete(replacement)
 
diff --git a/spec/unit/dry/inflector_spec.rb b/spec/unit/dry/inflector_spec.rb
index 4153a13..316333a 100644
--- a/spec/unit/dry/inflector_spec.rb
+++ b/spec/unit/dry/inflector_spec.rb
@@ -14,4 +14,19 @@
       expect(inflector.method(:inspect)).to eql(inflector.method(:to_s))
     end
   end
+
+  describe "#freeze" do
+    before(:each) do
+      inflector.freeze
+    end
+
+    it "freezes an inflections" do
+      expect { inflector.inflections.plural("ooh", "ooh") }.to raise_error(FrozenError, "can't modify a frozen inflection")
+      expect { inflector.inflections.singular("ooh", "ooh") }.to raise_error(FrozenError, "can't modify a frozen inflection")
+      expect { inflector.inflections.irregular("ooh", "ooh") }.to raise_error(FrozenError, "can't modify a frozen inflection")
+      expect { inflector.inflections.uncountable("ooh") }.to raise_error(FrozenError, "can't modify a frozen inflection")
+      expect { inflector.inflections.acronym("ooh") }.to raise_error(FrozenError, "can't modify a frozen inflection")
+      expect { inflector.inflections.human("barbra", "streisand") }.to raise_error(FrozenError, "can't modify a frozen inflection")
+    end
+  end
 end