diff --git a/Manifest b/Manifest
deleted file mode 100644
index c2e11dcb..00000000
--- a/Manifest
+++ /dev/null
@@ -1,8 +0,0 @@
-Rakefile
-README.md
-LICENSE
-lib/jwt.rb
-lib/jwt/json.rb
-spec/spec_helper.rb
-spec/jwt_spec.rb
-Manifest
diff --git a/lib/jwt/claims_validator.rb b/lib/jwt/claims_validator.rb
new file mode 100644
index 00000000..8891adfb
--- /dev/null
+++ b/lib/jwt/claims_validator.rb
@@ -0,0 +1,33 @@
+require_relative './error'
+
+module JWT
+  class ClaimsValidator
+    INTEGER_CLAIMS = %i[
+      exp
+      iat
+      nbf
+    ].freeze
+
+    def initialize(payload)
+      @payload = payload.each_with_object({}) { |(k, v), h| h[k.to_sym] = v }
+    end
+
+    def validate!
+      validate_int_claims
+
+      true
+    end
+
+    private
+
+    def validate_int_claims
+      INTEGER_CLAIMS.each do |claim|
+        validate_is_int(claim) if @payload.key?(claim)
+      end
+    end
+
+    def validate_is_int(claim)
+      raise InvalidPayload, "#{claim} claim must be an Integer but it is a #{@payload[claim].class}" unless @payload[claim].is_a?(Integer)
+    end
+  end
+end
diff --git a/lib/jwt/encode.rb b/lib/jwt/encode.rb
index 8769e7f4..bda51bbd 100644
--- a/lib/jwt/encode.rb
+++ b/lib/jwt/encode.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
+require_relative './claims_validator'
+
 # JWT::Encode module
 module JWT
   # Encoding logic for JWT
   class Encode
     ALG_NONE = 'none'.freeze
     ALG_KEY  = 'alg'.freeze
-    EXP_KEY  = 'exp'.freeze
-    EXP_KEYS = [EXP_KEY, EXP_KEY.to_sym].freeze
 
     def initialize(options)
       @payload   = options[:payload]
@@ -22,18 +22,6 @@ def segments
 
     private
 
-    def validate_payload!
-      return unless @payload && @payload.is_a?(Hash)
-
-      validate_exp!
-    end
-
-    def validate_exp!
-      return if EXP_KEYS.all? { |key| !@payload.key?(key) || @payload[key].is_a?(Integer) }
-
-      raise InvalidPayload, 'exp claim must be an integer'
-    end
-
     def encoded_header
       @encoded_header ||= encode_header
     end
@@ -55,7 +43,10 @@ def encode_header
     end
 
     def encode_payload
-      validate_payload!
+      if @payload && @payload.is_a?(Hash)
+        ClaimsValidator.new(@payload).validate!
+      end
+
       encode(@payload)
     end
 
diff --git a/spec/jwt/claims_validator_spec.rb b/spec/jwt/claims_validator_spec.rb
new file mode 100644
index 00000000..b5a04379
--- /dev/null
+++ b/spec/jwt/claims_validator_spec.rb
@@ -0,0 +1,45 @@
+require 'spec_helper'
+require 'jwt/claims_validator'
+
+RSpec.describe JWT::ClaimsValidator do
+  describe '#validate!' do
+    it 'returns true if the payload is valid' do
+      valid_payload = { 'exp' => 12345 }
+      subject = described_class.new(valid_payload)
+
+      expect(subject.validate!).to eq(true)
+    end
+
+    shared_examples_for 'an integer claim' do |claim|
+      it "raises an error when the value of the #{claim} claim is a string" do
+        subject = described_class.new({ claim => '1' })
+        expect { subject.validate! }.to raise_error JWT::InvalidPayload
+      end
+
+      it "raises an error when the value of the #{claim} claim is a Time object" do
+        subject = described_class.new({ claim => Time.now })
+        expect { subject.validate! }.to raise_error JWT::InvalidPayload
+      end
+
+      it "validates the #{claim} claim when the key is either a string or a symbol" do
+        symbol = described_class.new({ claim.to_sym => true })
+        expect { symbol.validate! }.to raise_error JWT::InvalidPayload
+
+        string = described_class.new({ claim.to_s => true })
+        expect { string.validate! }.to raise_error JWT::InvalidPayload
+      end
+    end
+
+    context 'exp claim' do
+      it_should_behave_like 'an integer claim', :exp
+    end
+
+    context 'iat claim' do
+      it_should_behave_like 'an integer claim', :iat
+    end
+
+    context 'nbf claim' do
+      it_should_behave_like 'an integer claim', :nbf
+    end
+  end
+end
diff --git a/spec/jwt_spec.rb b/spec/jwt_spec.rb
index 17c9ae36..1592c731 100644
--- a/spec/jwt_spec.rb
+++ b/spec/jwt_spec.rb
@@ -60,30 +60,21 @@
   end
 
   context 'payload validation' do
-    subject { JWT.encode(payload, nil, 'none') }
-    let(:payload) { { 'exp' => exp } }
+    it 'validates the payload with the ClaimsValidator if the payload is a hash' do
+      validator = double()
+      expect(JWT::ClaimsValidator).to receive(:new) { validator }
+      expect(validator).to receive(:validate!) { true }
 
-    context 'when exp is given as a non Integer' do
-      let(:exp) { Time.now.to_i.to_s }
-      it 'raises an JWT::InvalidPayload error' do
-        expect { subject }.to raise_error(JWT::InvalidPayload, 'exp claim must be an integer')
-      end
-    end
-
-    context 'when exp is given as an Integer' do
-      let(:exp) { 1234 }
-
-      it 'encodes the payload' do
-        expect(subject).to be_a(String)
-      end
+      payload = {}
+      JWT.encode payload, "secret", JWT::Algos::Hmac::SUPPORTED.sample
     end
 
-    context 'when the key for exp is a symbol' do
-      let(:payload) { { :exp => 'NotAInteger' } }
+    it 'does not validate the payload if it is not present' do
+      validator = double()
+      expect(JWT::ClaimsValidator).not_to receive(:new) { validator }
 
-      it 'raises an JWT::InvalidPayload error' do
-        expect { subject }.to raise_error(JWT::InvalidPayload, 'exp claim must be an integer')
-      end
+      payload = nil
+      JWT.encode payload, "secret", JWT::Algos::Hmac::SUPPORTED.sample
     end
   end