diff --git a/.builds/apple.yml b/.builds/apple.yml
index 946ffe80..26885c28 100644
--- a/.builds/apple.yml
+++ b/.builds/apple.yml
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Unlicense OR MIT
 image: debian/testing
 packages:
  - clang
diff --git a/.builds/freebsd.yml b/.builds/freebsd.yml
index 080ef05c..7ad7b5df 100644
--- a/.builds/freebsd.yml
+++ b/.builds/freebsd.yml
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Unlicense OR MIT
 image: freebsd/11.x
 packages:
  - libX11
diff --git a/.builds/linux.yml b/.builds/linux.yml
index 1124c19d..8951b8fc 100644
--- a/.builds/linux.yml
+++ b/.builds/linux.yml
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Unlicense OR MIT
 image: debian/testing
 packages:
  - curl
diff --git a/.builds/openbsd.yml b/.builds/openbsd.yml
index bee28741..a89e9176 100644
--- a/.builds/openbsd.yml
+++ b/.builds/openbsd.yml
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Unlicense OR MIT
 image: openbsd/latest
 packages:
  - libxkbcommon