diff --git a/.gitignore b/.gitignore
index 94851d6..87e11ec 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 src/cmd/apt_query/apt_query*
-*.log
\ No newline at end of file
+apt_query*
+*.log
diff --git a/install_and_cache_pkgs.sh b/install_and_cache_pkgs.sh
index 1a544ad..c310b0f 100755
--- a/install_and_cache_pkgs.sh
+++ b/install_and_cache_pkgs.sh
@@ -42,12 +42,7 @@ if [ -n "${add_repository}" ]; then
 fi
 
 log "Updating APT package list..."
-if [[ -z "$(find -H /var/lib/apt/lists -maxdepth 0 -mmin -5)" ]]; then
-  sudo apt-fast update > /dev/null
-  log "done"
-else
-  log "skipped (fresh within at least 5 minutes)"
-fi
+update_apt_lists_if_stale
 
 log_empty_line
 
diff --git a/lib.sh b/lib.sh
index 755d939..71a7b58 100755
--- a/lib.sh
+++ b/lib.sh
@@ -135,6 +135,34 @@ function get_tar_relpath {
   fi
 }
 
+###############################################################################
+# Updates APT package lists if they are stale (modified more than 5 minutes ago).
+# This ensures compatibility with environments like nektos/act where package lists
+# may be empty or stale. Only runs when ACT environment variable is set (nektos/act)
+# to avoid slowing down normal GitHub Actions runs.
+# Arguments:
+#   None
+# Returns:
+#   None
+###############################################################################
+function update_apt_lists_if_stale {
+  # Only check for stale package lists when running in nektos/act
+  # GitHub Actions runners have fresh package lists, so skip this overhead
+  if [ "${ACT}" = "true" ]; then
+    if [[ -z "$(find -H /var/lib/apt/lists -maxdepth 0 -mmin -5 2>/dev/null)" ]]; then
+      log "APT package lists are stale, updating..."
+      if command -v apt-fast > /dev/null 2>&1; then
+        sudo apt-fast update > /dev/null 2>&1 || sudo apt update > /dev/null 2>&1 || true
+      else
+        sudo apt update > /dev/null 2>&1 || true
+      fi
+      log "APT package lists updated"
+    else
+      log "APT package lists are fresh (within 5 minutes), skipping update"
+    fi
+  fi
+}
+
 function log { echo "${@}"; }
 function log_err { >&2 echo "${@}"; }
 
diff --git a/pre_cache_action.sh b/pre_cache_action.sh
index 5cb64cb..105135f 100755
--- a/pre_cache_action.sh
+++ b/pre_cache_action.sh
@@ -32,6 +32,10 @@ input_packages="${@:6}"
 
 # Trim commas, excess spaces, and sort.
 log "Normalizing package list..."
+
+# Ensure APT package lists are updated if stale (for nektos/act compatibility)
+update_apt_lists_if_stale
+
 packages="$(get_normalized_package_list "${input_packages}")"
 log "done"