diff --git a/.github/workflows/python-builder.yml b/.github/workflows/python-builder.yml
index d58cb58..5579998 100644
--- a/.github/workflows/python-builder.yml
+++ b/.github/workflows/python-builder.yml
@@ -38,7 +38,7 @@ jobs:
       - name: Generate execution matrix
         id: generate-matrix
         run: |
-          $configurations = "${{ github.event.inputs.platforms }}".Split(",").Trim()
+          $configurations = "${{ github.event.inputs.platforms || 'ubuntu-18.04,ubuntu-20.04,macos-10.15,windows-2019_x64,windows-2019_x86' }}".Split(",").Trim()
           $matrix = @()
 
           foreach ($configuration in $configurations) {