diff --git a/Gemfile.lock b/Gemfile.lock
index a47be0e..b98c17f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,18 +2,16 @@ PATH
   remote: .
   specs:
     psychometric (0.1.9)
-      httparty (~> 0.16.4)
+      httparty (>= 0.16.4, < 0.22.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
     diff-lcs (1.3)
-    httparty (0.16.4)
-      mime-types (~> 3.0)
+    httparty (0.21.0)
+      mini_mime (>= 1.0.0)
       multi_xml (>= 0.5.2)
-    mime-types (3.3)
-      mime-types-data (~> 3.2015)
-    mime-types-data (3.2019.0904)
+    mini_mime (1.1.2)
     multi_xml (0.6.0)
     rake (13.0.1)
     rspec (3.8.0)
diff --git a/psychometric.gemspec b/psychometric.gemspec
index 866dc14..fb9530a 100644
--- a/psychometric.gemspec
+++ b/psychometric.gemspec
@@ -36,7 +36,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "httparty", "~> 0.16.4"
+  spec.add_dependency "httparty", ">= 0.16.4", "< 0.22.0"
 
   spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "rake", "~> 13.0"