diff --git a/action.yml b/action.yml
index 7d3889c..4cab487 100644
--- a/action.yml
+++ b/action.yml
@@ -258,15 +258,15 @@ runs:
             export NIX_INSTALLER_URL=${{ inputs.nix-installer-url }}
           else
             if [ -n "${{ inputs.nix-installer-pr }}" ]; then
-              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/pr/${{ inputs.nix-installer-pr }}
+              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/pr/${{ inputs.nix-installer-pr }}?ci=github
             elif [ -n "${{ inputs.nix-installer-tag }}" ]; then
-              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/tag/${{ inputs.nix-installer-tag }}
+              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/tag/${{ inputs.nix-installer-tag }}?ci=github
             elif [ -n "${{ inputs.nix-installer-revision }}" ]; then
-              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/rev/${{ inputs.nix-installer-revision }}
+              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/rev/${{ inputs.nix-installer-revision }}?ci=github
             elif [ -n "${{ inputs.nix-installer-branch }}" ]; then
-              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/branch/${{ inputs.nix-installer-branch }}
+              export NIX_INSTALLER_URL=https://install.determinate.systems/nix/branch/${{ inputs.nix-installer-branch }}?ci=github
             else
-              export NIX_INSTALLER_URL=https://install.determinate.systems/nix
+              export NIX_INSTALLER_URL=https://install.determinate.systems/nix?ci=github
             fi
           fi
           echo "Set NIX_INSTALLER_URL=$NIX_INSTALLER_URL"