diff --git a/fixtures/rails_3_2_12/spec/controllers/other_things_controller_spec.rb b/fixtures/rails_3_2_12/spec/controllers/other_things_controller_spec.rb
index ebbf0f40..99a5b488 100644
--- a/fixtures/rails_3_2_12/spec/controllers/other_things_controller_spec.rb
+++ b/fixtures/rails_3_2_12/spec/controllers/other_things_controller_spec.rb
@@ -13,7 +13,7 @@ def request(opts = {})
     options = opts.merge(
       {
         'HTTPS' => 'on',
-        'HTTP_USER_AGENT' => "Mozilla/5.0 (compatible; MSIE 10.6; Windows NT 6.1; Trident/5.0; InfoPath.2; SLCC1; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 2.0.50727) 3gpp-gba UNTRUSTED/1.0"
+        'HTTP_USER_AGENT' => "Mozilla/5.0 (Macintosh; Intel Mac OS X 1084) AppleWebKit/537.22 (KHTML like Gecko) Chrome/25.0.1364.99 Safari/537.22"
       }
     )
 
diff --git a/fixtures/rails_4_1_8/spec/controllers/other_things_controller_spec.rb b/fixtures/rails_4_1_8/spec/controllers/other_things_controller_spec.rb
index 10bcc8cd..6b602565 100644
--- a/fixtures/rails_4_1_8/spec/controllers/other_things_controller_spec.rb
+++ b/fixtures/rails_4_1_8/spec/controllers/other_things_controller_spec.rb
@@ -13,7 +13,7 @@ def request(opts = {})
     options = opts.merge(
       {
         'HTTPS' => 'on',
-        'HTTP_USER_AGENT' => "Mozilla/5.0 (compatible; MSIE 10.6; Windows NT 6.1; Trident/5.0; InfoPath.2; SLCC1; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 2.0.50727) 3gpp-gba UNTRUSTED/1.0"
+        'HTTP_USER_AGENT' => "Mozilla/5.0 (Macintosh; Intel Mac OS X 1084) AppleWebKit/537.22 (KHTML like Gecko) Chrome/25.0.1364.99 Safari/537.22"
       }
     )
 
diff --git a/lib/secure_headers/headers/content_security_policy.rb b/lib/secure_headers/headers/content_security_policy.rb
index 88214b15..407c663b 100644
--- a/lib/secure_headers/headers/content_security_policy.rb
+++ b/lib/secure_headers/headers/content_security_policy.rb
@@ -1,6 +1,7 @@
 require 'uri'
 require 'base64'
 require 'securerandom'
+require 'user_agent_parser'
 
 module SecureHeaders
   class ContentSecurityPolicyBuildError < StandardError; end
@@ -205,8 +206,12 @@ def translate_dir_value val
       elsif %{self none}.include?(val)
         "'#{val}'"
       elsif val == 'nonce'
-        self.class.set_nonce(@controller, nonce)
-        ["'nonce-#{nonce}'", "'unsafe-inline'"]
+        if supports_nonces?(@ua)
+          self.class.set_nonce(@controller, nonce)
+          ["'nonce-#{nonce}'", "'unsafe-inline'"]
+        else
+          "'unsafe-inline'"
+        end
       else
         val
       end
@@ -258,5 +263,10 @@ def non_default_directives
     def build_directive(key)
       "#{self.class.symbol_to_hyphen_case(key)} #{@config[key].join(" ")}; "
     end
+
+    def supports_nonces?(user_agent)
+      parsed_ua = UserAgentParser.parse(user_agent)
+      ["Chrome", "Opera", "Firefox"].include?(parsed_ua.family)
+    end
   end
 end
diff --git a/secure_headers.gemspec b/secure_headers.gemspec
index a6a28afe..5353828f 100644
--- a/secure_headers.gemspec
+++ b/secure_headers.gemspec
@@ -19,5 +19,6 @@ Gem::Specification.new do |gem|
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
   gem.require_paths = ["lib"]
   gem.add_development_dependency "rake"
+  gem.add_dependency "user_agent_parser"
   gem.post_install_message = "Warning: lambda config values will be broken until you add |controller|. e.g. :enforce => lambda { |controller| some_expression }"
 end
diff --git a/spec/lib/secure_headers/headers/content_security_policy_spec.rb b/spec/lib/secure_headers/headers/content_security_policy_spec.rb
index 7ca0df6c..53a447c1 100644
--- a/spec/lib/secure_headers/headers/content_security_policy_spec.rb
+++ b/spec/lib/secure_headers/headers/content_security_policy_spec.rb
@@ -17,7 +17,8 @@ module SecureHeaders
     FIREFOX_23 = "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:23.0) Gecko/20131011 Firefox/23.0"
     CHROME = "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_4; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.99 Safari/533.4"
     CHROME_25 = "Mozilla/5.0 (Macintosh; Intel Mac OS X 1084) AppleWebKit/537.22 (KHTML like Gecko) Chrome/25.0.1364.99 Safari/537.22"
-
+    SAFARI = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A"
+    OPERA = "Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16"
 
     def request_for user_agent, request_uri=nil, options={:ssl => false}
       double(:ssl? => options[:ssl], :env => {'HTTP_USER_AGENT' => user_agent}, :url => (request_uri || 'http://areallylongdomainexample.com') )
@@ -184,11 +185,33 @@ def request_for user_agent, request_uri=nil, options={:ssl => false}
       end
 
       context "when using a nonce" do
-        it "adds a nonce and unsafe-inline to the script-src value" do
+        it "adds a nonce and unsafe-inline to the script-src value when using chrome" do
           header = ContentSecurityPolicy.new(default_opts.merge(:script_src => "self nonce"), :request => request_for(CHROME))
           expect(header.value).to include("script-src 'self' 'nonce-#{header.nonce}' 'unsafe-inline'")
         end
 
+        it "adds a nonce and unsafe-inline to the script-src value when using firefox" do
+          header = ContentSecurityPolicy.new(default_opts.merge(:script_src => "self nonce"), :request => request_for(FIREFOX))
+          expect(header.value).to include("script-src 'self' 'nonce-#{header.nonce}' 'unsafe-inline'")
+        end
+
+        it "adds a nonce and unsafe-inline to the script-src value when using opera" do
+          header = ContentSecurityPolicy.new(default_opts.merge(:script_src => "self nonce"), :request => request_for(OPERA))
+          expect(header.value).to include("script-src 'self' 'nonce-#{header.nonce}' 'unsafe-inline'")
+        end
+
+        it "does not add a nonce and unsafe-inline to the script-src value when using Safari" do
+          header = ContentSecurityPolicy.new(default_opts.merge(:script_src => "self nonce"), :request => request_for(SAFARI))
+          expect(header.value).to include("script-src 'self' 'unsafe-inline'")
+          expect(header.value).not_to include("nonce")
+        end
+
+        it "does not add a nonce and unsafe-inline to the script-src value when using IE" do
+          header = ContentSecurityPolicy.new(default_opts.merge(:script_src => "self nonce"), :request => request_for(IE))
+          expect(header.value).to include("script-src 'self' 'unsafe-inline'")
+          expect(header.value).not_to include("nonce")
+        end
+
         it "adds a nonce and unsafe-inline to the style-src value" do
           header = ContentSecurityPolicy.new(default_opts.merge(:style_src => "self nonce"), :request => request_for(CHROME))
           expect(header.value).to include("style-src 'self' 'nonce-#{header.nonce}' 'unsafe-inline'")