diff --git a/lib/send_grid/api_header.rb b/lib/send_grid/api_header.rb
index 34449c1..1d4893c 100644
--- a/lib/send_grid/api_header.rb
+++ b/lib/send_grid/api_header.rb
@@ -27,7 +27,7 @@ def add_filter_setting(fltr, setting, val)
   end
 
   def to_json
-    @data.to_json
+    JSON.generate(@data, {:indent => " ", :space => "", :space_before => "", :object_nl => "", :array_nl => ""})
   end
 
   def standard_smtp(enabled = false)
diff --git a/spec/api_header_spec.rb b/spec/api_header_spec.rb
index 230ddf9..20bcf45 100644
--- a/spec/api_header_spec.rb
+++ b/spec/api_header_spec.rb
@@ -9,32 +9,32 @@
 
     it "contains 1 recipient (as array)" do
       header.add_recipients 'email@email.com'
-      header.to_json.should eql '{"to":["email@email.com"]}'
+      header.to_json.should eql '{ "to":[  "email@email.com"]}'
     end
 
     it "contaions an array of recipients" do
       header.add_recipients %w(email1@email.com email2@email.com)
-      header.to_json.should eql '{"to":["email1@email.com","email2@email.com"]}'
+      header.to_json.should eql '{ "to":[  "email1@email.com",  "email2@email.com"]}'
     end
 
     it "contains substitution" do
       header.substitute :var1, 'Hello'
-      header.to_json.should eql '{"sub":{"var1":["Hello"]}}'
+      header.to_json.should eql '{ "sub":{  "var1":[   "Hello"]}}'
     end
 
     it "contains uniq args" do
       header.uniq_args :arg1 => 'val1'
-      header.to_json.should eql '{"unique_args":{"arg1":"val1"}}'
+      header.to_json.should eql '{ "unique_args":{  "arg1":"val1"}}'
     end
 
     it "contains category" do
       header.category 'category_name'
-      header.to_json.should eql '{"category":"category_name"}'
+      header.to_json.should eql '{ "category":"category_name"}'
     end
 
     it "contains filter settings" do
       header.add_filter_setting :filter1, :setting1, 'val1'
-      header.to_json.should eql '{"filters":{"filter1":{"settings":{"setting1":"val1"}}}}'
+      header.to_json.should eql '{ "filters":{  "filter1":{   "settings":{    "setting1":"val1"}}}}'
     end
   end
 end
diff --git a/spec/mailer_spec.rb b/spec/mailer_spec.rb
index d3039fa..218f7dc 100644
--- a/spec/mailer_spec.rb
+++ b/spec/mailer_spec.rb
@@ -4,7 +4,7 @@
   describe 'email with multiple recipients' do
     it 'set correct recipients in X-SMTAPI header' do
       Mailer.email_with_multiple_recipients(%w(em1@email.com em2@email.com)).deliver.header.to_s.
-        should include('X-SMTPAPI: {"to":["em1@email.com","em2@email.com"]}')
+        should include('X-SMTPAPI: { "to":[  "em1@email.com",  "em2@email.com"]}')
     end
 
     it 'removes original TO header part' do
@@ -16,12 +16,12 @@
   describe '#open_tracking' do
     it 'set correct open tracking enabled X-SMTAPI header' do
       Mailer.email_open_tracking.deliver.header.to_s.
-        should include('"filters":{"opentrack":{"settings":{"enabled":1}}}')
+        should include(' "filters":{  "opentrack":{   "settings":{    "enabled":1}}}')
     end
 
     it 'set correct open tracking disabled X-SMTAPI header' do
       Mailer.email_open_tracking(false).deliver.header.to_s.
-        should include('"filters":{"opentrack":{"settings":{"enabled":0}}}')
+        should include(' "filters":{  "opentrack":{   "settings":{    "enabled":0}}}')
     end
 
     it 'set correct open tracking nil X-SMTAPI header' do