diff --git a/appveyor.yml b/appveyor.yml
index a662e20e1..a630a3a51 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,6 +1,10 @@
 os:
   - "WMF 5"
 
+environment:
+  CA_KEY:
+    secure: JQtUaB+zduPID8bzI5nfHRc2V6xYJiJp4mTHkE4W6broH8rznT1ypvn5orQ6YcGn
+
 branches:
   only:
     - master
@@ -18,6 +22,11 @@ install:
 
 build: false
 
+before_test:
+  - ps: Set-PSRepository -Name PSGallery -InstallationPolicy Trusted
+  - ps: Install-Module Coveralls -MinimumVersion 1.0.5 -Scope CurrentUser
+  - ps: Import-Module Coveralls
+
 test_script:
   - ps: |
       $testResultsFile = Join-Path $Env:APPVEYOR_BUILD_FOLDER TestResults.xml
@@ -38,3 +47,10 @@ test_script:
           $Error | Format-List * -Force
           exit 1;
       }
+      $ErrorActionPreference = 'Stop'
+      if (!(Test-Path Env:CA_KEY)) {
+          Write-Host 'CA_KEY not set! (Expected on PR builds.)'
+          return;
+      }
+      $coverageResult = Format-Coverage -Include (gci ..\src\* -include *.ps1,*.psm1) -CoverallsApiToken $ENV:CA_KEY -RootFolder ../ -BranchName $ENV:APPVEYOR_REPO_BRANCH
+      Publish-Coverage -Coverage $coverageResult