diff --git a/README.md b/README.md
index c0d1c3b..cd879d1 100644
--- a/README.md
+++ b/README.md
@@ -46,7 +46,7 @@ There are three kinds of version labels you can use.
 
 ### Cache scopes
 
-The cache is scoped to the packages given and the branch. The default branch cache is available to other branches.
+The cache is scoped to the packages given and the branch. The default branch cache is available to other branches. The cache key also includes runner image metadata (`ImageOS`, `ImageVersion`) when available so caches are invalidated as runner images change.
 
 ### Example workflow
 
diff --git a/pre_cache_action.sh b/pre_cache_action.sh
index 5cb64cb..4283bae 100755
--- a/pre_cache_action.sh
+++ b/pre_cache_action.sh
@@ -99,6 +99,17 @@ log "- CPU architecture is '${cpu_arch}'."
 
 value="${packages} @ ${version} ${force_update_inc}"
 
+# Include runner image metadata in cache key when available to avoid stale
+# cache hits when GitHub rotates images.
+if [ -n "${ImageOS}" ]; then
+  value="${value} image_os:${ImageOS}"
+  log "- Runner image OS '${ImageOS}' added to value."
+fi
+if [ -n "${ImageVersion}" ]; then
+  value="${value} image_version:${ImageVersion}"
+  log "- Runner image version '${ImageVersion}' added to value."
+fi
+
 # Include repositories in cache key to ensure different repos get different caches
 if [ -n "${add_repository}" ]; then
   value="${value} ${add_repository}"