diff --git a/Library/Homebrew/cask/cask.rb b/Library/Homebrew/cask/cask.rb
index 824993a865..69b4eeea5f 100644
--- a/Library/Homebrew/cask/cask.rb
+++ b/Library/Homebrew/cask/cask.rb
@@ -175,7 +175,7 @@ module Cask
         "url"            => url,
         "appcast"        => appcast,
         "version"        => version,
-        "installed"      => versions,
+        "installed"      => versions.last,
         "outdated"       => outdated?,
         "sha256"         => sha256,
         "artifacts"      => artifacts.map(&method(:to_h_gsubs)),
diff --git a/Library/Homebrew/test/cask/cmd/list_spec.rb b/Library/Homebrew/test/cask/cmd/list_spec.rb
index f1430ed3ad..8e8adb4070 100644
--- a/Library/Homebrew/test/cask/cmd/list_spec.rb
+++ b/Library/Homebrew/test/cask/cmd/list_spec.rb
@@ -91,7 +91,7 @@ describe Cask::Cmd::List, :cask do
     let(:casks) { ["local-caffeine", "local-transmission"] }
     let(:expected_output) {
       <<~EOS
-        [{"token":"local-caffeine","name":[],"desc":null,"homepage":"https://brew.sh/","url":"file:///usr/local/Homebrew/Library/Homebrew/test/support/fixtures/cask/caffeine.zip","appcast":null,"version":"1.2.3","installed":["1.2.3"],"outdated":false,"sha256":"67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94","artifacts":[["Caffeine.app"]],"caveats":null,"depends_on":{},"conflicts_with":null,"container":null,"auto_updates":null},{"token":"local-transmission","name":["Transmission"],"desc":"BitTorrent client","homepage":"https://transmissionbt.com/","url":"file:///usr/local/Homebrew/Library/Homebrew/test/support/fixtures/cask/transmission-2.61.dmg","appcast":null,"version":"2.61","installed":["2.61"],"outdated":false,"sha256":"e44ffa103fbf83f55c8d0b1bea309a43b2880798dae8620b1ee8da5e1095ec68","artifacts":[["Transmission.app"]],"caveats":null,"depends_on":{},"conflicts_with":null,"container":null,"auto_updates":null}]
+        [{"token":"local-caffeine","name":[],"desc":null,"homepage":"https://brew.sh/","url":"file:///usr/local/Homebrew/Library/Homebrew/test/support/fixtures/cask/caffeine.zip","appcast":null,"version":"1.2.3","installed":"1.2.3","outdated":false,"sha256":"67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94","artifacts":[["Caffeine.app"]],"caveats":null,"depends_on":{},"conflicts_with":null,"container":null,"auto_updates":null},{"token":"local-transmission","name":["Transmission"],"desc":"BitTorrent client","homepage":"https://transmissionbt.com/","url":"file:///usr/local/Homebrew/Library/Homebrew/test/support/fixtures/cask/transmission-2.61.dmg","appcast":null,"version":"2.61","installed":"2.61","outdated":false,"sha256":"e44ffa103fbf83f55c8d0b1bea309a43b2880798dae8620b1ee8da5e1095ec68","artifacts":[["Transmission.app"]],"caveats":null,"depends_on":{},"conflicts_with":null,"container":null,"auto_updates":null}]
       EOS
     }