diff --git a/lib/upload_security.rb b/lib/upload_security.rb
index 0a2acfdc031..45724735544 100644
--- a/lib/upload_security.rb
+++ b/lib/upload_security.rb
@@ -29,6 +29,11 @@ class UploadSecurity
     @@custom_public_types << type if !@@custom_public_types.include?(type)
   end
 
+  # used in tests
+  def self.reset_custom_public_types
+    @@custom_public_types = []
+  end
+
   def initialize(upload, opts = {})
     @upload = upload
     @opts = opts
diff --git a/spec/lib/upload_security_spec.rb b/spec/lib/upload_security_spec.rb
index 2ff1220b6b5..d154528f391 100644
--- a/spec/lib/upload_security_spec.rb
+++ b/spec/lib/upload_security_spec.rb
@@ -74,6 +74,7 @@ RSpec.describe UploadSecurity do
           it "returns false if the custom type has been added" do
             UploadSecurity.register_custom_public_type(type)
             expect(subject.should_be_secure?).to eq(false)
+            UploadSecurity.reset_custom_public_types
           end
         end
         describe "for_theme" do