diff --git a/Gemfile.lock b/Gemfile.lock
index ac738f5..0cb136c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -3,27 +3,26 @@ PATH
   specs:
     grpc-web (1.2.1)
       grpc (~> 1.0)
-      rack (>= 1.6.0, < 3.0)
+      rack (>= 1.6.0, < 4.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
     addressable (2.7.0)
       public_suffix (>= 2.0.2, < 5.0)
-    apparition (0.1.0)
-      backports
-      capybara (~> 3.12, < 4)
+    apparition (0.6.0)
+      capybara (~> 3.13, < 4)
       websocket-driver (>= 0.6.5)
     ast (2.4.0)
-    backports (3.15.0)
     byebug (11.0.1)
-    capybara (3.15.1)
+    capybara (3.38.0)
       addressable
+      matrix
       mini_mime (>= 0.1.3)
       nokogiri (~> 1.8)
       rack (>= 1.6.0)
       rack-test (>= 0.6.3)
-      regexp_parser (~> 1.2)
+      regexp_parser (>= 1.5, < 3.0)
       xpath (~> 3.2)
     coderay (1.1.2)
     crack (0.4.3)
@@ -39,6 +38,7 @@ GEM
     hashdiff (1.0.0)
     jaro_winkler (1.5.4)
     json (2.3.0)
+    matrix (0.4.2)
     method_source (0.9.2)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
@@ -54,11 +54,11 @@ GEM
       byebug (~> 11.0)
       pry (~> 0.10)
     public_suffix (4.0.1)
-    rack (2.0.9)
-    rack-cors (1.1.0)
+    rack (3.0.7)
+    rack-cors (2.0.0)
       rack (>= 2.0.0)
-    rack-test (1.1.0)
-      rack (>= 1.0, < 3)
+    rack-test (2.1.0)
+      rack (>= 1.3)
     rainbow (3.0.0)
     rake (13.0.1)
     regexp_parser (1.6.0)
diff --git a/grpc-web.gemspec b/grpc-web.gemspec
index 6f30f52..8a7750d 100644
--- a/grpc-web.gemspec
+++ b/grpc-web.gemspec
@@ -21,7 +21,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_dependency 'grpc', '~> 1.0'
-  spec.add_dependency 'rack', '>= 1.6.0', '< 3.0'
+  spec.add_dependency 'rack', '>= 1.6.0', '< 4.0'
 
   spec.add_development_dependency 'apparition'
   spec.add_development_dependency 'pry-byebug'