diff --git a/futurella/challenge/Gemfile.lock b/futurella/challenge/Gemfile.lock
index 052e274..1b5e74d 100644
--- a/futurella/challenge/Gemfile.lock
+++ b/futurella/challenge/Gemfile.lock
@@ -3,33 +3,35 @@ PATH
   specs:
     challenge (0.0.0)
       optimist (~> 3.0.0)
-      sinatra (~> 2.0.5)
+      sinatra (>= 2.0.5, < 3.1.0)
       singlogger (~> 0.0.0)
       thin (~> 1.7.2)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    daemons (1.3.1)
+    daemons (1.4.1)
     docile (1.1.5)
     eventmachine (1.2.7)
     json (2.1.0)
-    mustermann (1.0.3)
-    optimist (3.0.0)
+    mustermann (3.0.0)
+      ruby2_keywords (~> 0.0.1)
+    optimist (3.0.1)
     power_assert (1.1.3)
-    rack (2.0.6)
-    rack-protection (2.0.5)
+    rack (2.2.4)
+    rack-protection (3.0.4)
       rack
     rake (10.5.0)
+    ruby2_keywords (0.0.5)
     simplecov (0.14.1)
       docile (~> 1.1.0)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sinatra (2.0.5)
-      mustermann (~> 1.0)
-      rack (~> 2.0)
-      rack-protection (= 2.0.5)
+    sinatra (3.0.4)
+      mustermann (~> 3.0)
+      rack (~> 2.2, >= 2.2.4)
+      rack-protection (= 3.0.4)
       tilt (~> 2.0)
     singlogger (0.0.1)
     test-unit (3.2.9)
@@ -38,7 +40,7 @@ GEM
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)
-    tilt (2.0.9)
+    tilt (2.0.11)
 
 PLATFORMS
   ruby
diff --git a/futurella/challenge/challenge.gemspec b/futurella/challenge/challenge.gemspec
index e9deb86..fa45d28 100644
--- a/futurella/challenge/challenge.gemspec
+++ b/futurella/challenge/challenge.gemspec
@@ -28,7 +28,7 @@ Gem::Specification.new do |spec|
   #spec.add_dependency 'hexhelper',  '~> 0.0.2'
   spec.add_dependency 'optimist', '~> 3.0.0'
   #spec.add_dependency 'salsa20', '~> 0.1.3'
-  spec.add_dependency 'sinatra', '~> 2.0.5'
+  spec.add_dependency 'sinatra', '>= 2.0.5', '< 3.1.0'
   spec.add_dependency 'singlogger', '~> 0.0.0'
   spec.add_dependency 'thin', '~> 1.7.2'
 end